Jesus Christ lol Parmatma and Parmatam mean the same thing. That which is singular is simultaneously plural.
Page 13, Line 3
ਸਹਸ ਤਵ ਨੈਨ ਨਨ ਨੈਨ ਹਹਿ ਤੋਹਿ ਕਉ ਸਹਸ ਮੂਰਤਿ ਨਨਾ ਏਕ ਤਹੀ ॥
सहस तव नैन नन नैन हहि तोहि कउ सहस मूरति नना एक तोही ॥
Sahas ṯav nain nan nain hėh ṯohi ka▫o sahas mūraṯ nanā ek ṯohī.
You have thousands of eyes, and yet You have no eyes. You have thousands of forms, and yet You do not have even one.
Guru Nanak Dev - view Shabad/Paurhi/Salok
The intellectually dishonest use of previously existing vocabulary is an appealing theory to some but Ram is both the King of Ayodhya and the Almighty One. Ram means and always meant both simultaneously. Another example is Krishna who is sometimes referred to gopi-seducer, four-armed Lord in Gurbani, which carry all meanings. Just like Guru Nanak has come to mean both the 1st Guru and the Almighty One. For some future prophet/Guru/Avatar/messenger of God to then preach that one needs to dissolve one's ego to reach Guru Nanak, would not be surprising. He need not invent new vocabulary as the older vocabulary already covers what he is talking about.
If Guru Sahibs were looking specifically for words for their vision, then there were several, Ishvar, Parmatam, Brahman, etc. already available that were disconnected from any avatars, which of course they do use often (especially Brahman). But these are devoid of personal characteristics and so do not seem to appeal to Guru Sahibs as much as words that carry personal characteristics. Again there was no need invent any words. And to claim that they used old words to mean something entirely different, is simply accusing Gurus of deception. Gurus were not trying to deceive Hindus into Sikh fold by using words like Ram, Mohan, Gobind, Krishna, Chaturbhuj and Guru that they did not believe in. They believed in them and were honest about what they felt. This drew people in. Honesty and truth draw people in.
Such words carry familiar images of Krishna the herder, the seducer, Ram the righteous warrior, make for great imagery and thus would naturally appeal to everyone (because they stick in the mind - every kid on the block knows the stories) including the authors of Sri Guru Granth Sahib Ji. Their vision of God is personal. They use the pronoun "You" (Krishna) as opposed to "It" (Brahman), etc.
An example of this personal relationship:
Guru Granth Sahib Page 1197
ਰਾਗੁ ਸਾਰਗ ਚਉਪਦੇ ਮਹਲਾ ੧ ਘਰੁ ੧
रागु सारग चउपदे महला १ घरु १
Rāg sārag cẖa▫upḏe mėhlā 1 gẖar 1
Raag Saarang, Chau-Padas, First Mehl, First House:
ੴ ਸਤਿ ਨਾਮੁ ਕਰਤਾ ਪੁਰਖੁ ਨਿਰਭਉ ਨਿਰਵੈਰੁ ਅਕਾਲ ਮੂਰਤਿ ਅਜੂਨੀ ਸੈਭੰ ਗੁਰ ਪ੍ਰਸਾਦਿ ॥
ੴ सति नामु करता पुरखु निरभउ निरवैरु अकाल मूरति अजूनी सैभं गुर प्रसादि ॥
Ik▫oaʼnkār saṯ nām karṯā purakẖ nirbẖa▫o nirvair akāl mūraṯ ajūnī saibẖaʼn gur parsāḏ.
One Universal Creator God. Truth Is The Name. Creative Being Personified. No Fear. No Hatred. Image Of The Undying. Beyond Birth. Self-Existent. By Guru's Grace:
ਅਪੁਨੇ ਠਾਕੁਰ ਕੀ ਹਉ ਚੇਰੀ ॥
अपुने ठाकुर की हउ चेरी ॥
Apune ṯẖākur kī ha▫o cẖerī.
I am the hand-maiden of my Lord and Master.
ਚਰਨ ਗਹੇ ਜਗਜੀਵਨ ਪ੍ਰਭ ਕੇ ਹਉਮੈ ਮਾਰਿ ਨਿਬੇਰੀ ॥੧॥ ਰਹਾਉ ॥
चरन गहे जगजीवन प्रभ के हउमै मारि निबेरी ॥१॥ रहाउ ॥
Cẖaran gahe jagjīvan parabẖ ke ha▫umai mār niberī. ||1|| rahā▫o.
I have grasped the Feet of God, the Life of the world. He has killed and eradicated my egotism. ||1||Pause||
ਪੂਰਨ ਪਰਮ ਜੋਤਿ ਪਰਮੇਸਰ ਪ੍ਰੀਤਮ ਪ੍ਰਾਨ ਹਮਾਰੇ ॥
पूरन परम जोति परमेसर प्रीतम प्रान हमारे ॥
Pūran param joṯ parmesar parīṯam parān hamāre.
He is the Perfect, Supreme Light, the Supreme Lord God, my Beloved, my Breath of Life.
ਮੋਹਨ ਮੋਹਿ ਲੀਆ ਮਨੁ ਮੇਰਾ ਸਮਝਸਿ ਸਬਦੁ ਬੀਚਾਰੇ ॥੧॥
मोहन मोहि लीआ मनु मेरा समझसि सबदु बीचारे ॥१॥
Mohan mohi lī▫ā man merā samjẖas sabaḏ bīcẖāre. ||1||
The Fascinating Lord has fascinated my mind; contemplating the Word of the Shabad, I have come to understand. ||1||
ਮੋਹਨ - Krishna being referred to as the lover, seducer. He was very charming and every girl in the village wanted to be his bride. The soul-bride metaphor that comes at the end of the shabad only makes sense in light of Krishna's life story.
The Seducer (Krishna/God) has seduced my mind and I have come to understand.
ਮਨਮੁਖ ਹੀਨ ਹੋਛੀ ਮਤਿ ਝੂਠੀ ਮਨਿ ਤਨਿ ਪੀਰ ਸਰੀਰੇ ॥
मनमुख हीन होछी मति झूठी मनि तनि पीर सरीरे ॥
Manmukẖ hīn hocẖẖī maṯ jẖūṯẖī man ṯan pīr sarīre.
The worthless self-willed manmukh, with false and shallow understanding - his mind and body are held in pain's grip.
ਜਬ ਕੀ ਰਾਮ ਰੰਗੀਲੈ ਰਾਤੀ ਰਾਮ ਜਪਤ ਮਨ ਧੀਰੇ ॥੨॥
जब की राम रंगीलै राती राम जपत मन धीरे ॥२॥
Jab kī rām rangīlai rāṯī rām japaṯ man ḏẖīre. ||2||
Since I came to be imbued with the Love of my Beautiful Lord, I meditate on the Lord, and my mind is encouraged. ||2||
ਹਉਮੈ ਛੋਡਿ ਭਈ ਬੈਰਾਗਨਿ ਤਬ ਸਾਚੀ ਸੁਰਤਿ ਸਮਾਨੀ ॥
हउमै छोडि भई बैरागनि तब साची सुरति समानी ॥
Ha▫umai cẖẖod bẖa▫ī bairāgan ṯab sācẖī suraṯ samānī.
Abandoning egotism, I have become detached. And now, I absorb true intuitive understanding.
ਅਕੁਲ ਨਿਰੰਜਨ ਸਿਉ ਮਨੁ ਮਾਨਿਆ ਬਿਸਰੀ ਲਾਜ ਲਕਾਨੀ ॥੩॥
अकुल निरंजन सिउ मनु मानिआ बिसरी लाज लोकानी ॥३॥
Akul niranjan si▫o man māni▫ā bisrī lāj lokānī. ||3||
The mind is pleased and appeased by the Pure, Immaculate Lord; the opinions of other people are irrelevant. ||3||
ਭੂਰ ਭਵਿਖ ਨਾਹੀ ਤੁਮ ਜੈਸੇ ਮੇਰੇ ਪ੍ਰੀਤਮ ਪ੍ਰਾਨ ਅਧਾਰਾ ॥
भूर भविख नाही तुम जैसे मेरे प्रीतम प्रान अधारा ॥
Bẖūr bẖavikẖ nāhī ṯum jaise mere parīṯam parān aḏẖārā.
There is no other like You, in the past or in the future, O my Beloved, my Breath of Life, my Support.
ਹਰਿ ਕੈ ਨਾਮਿ ਰਤੀ ਸੋਹਾਗਨਿ ਨਾਨਕ ਰਾਮ ਭਤਾਰਾ ॥੪॥੧॥
हरि कै नामि रती सोहागनि नानक राम भतारा ॥४॥१॥
Har kai nām raṯī sohāgan Nānak rām bẖaṯārā. ||4||1||
The soul-bride is imbued with the Name of the Lord; O Nanak, the Lord is her Husband. ||4||1||
Cheers