Thats the problem.
For arabic we have some reference i.e quran but not much for farsi
the other problem that for almost all arabic word there is some other word in farsi , and urdu being the bridge uses and incorporate all those verity of words.
I am not certain about ghulam’s origin but closest i think is the word ‘Ghulman’ which is used for male servent in heaven 
not just Arabic or Farsi, Urdo also has many Turkish and Sansikrat words.
For instance ?
Please tell us some turkish, sansikrit words used in urdu :)
Re: How to distinguish Arbi and Farsi words used in urdu ?
Turkish=Malmal,bulbul,resham etc
Sanskrit=Sagar,Akash,Jal(these are borrowed directly from Sanskrit, dunno if used by common Urdu speaker, though i found tham in many Pakistani songs and band names)
there is a big share of words that have formed due to corruption of Sanskrit words.
ek(Ekkam),Do(Dwiyam),Tin(Thritiya).......
aag(Agni),saap(Sarpa), bazu(Baahu), tu/tum(Twayam), ghar(Ghriham), kaha(Kutra), raat(Ratrim), kaam(Karya) etc
there are a lot of French and Portuguese words too.
you knew Sabun and Almirah are Portuguese words??
i studied Sanskrit for 3 long years, and i sucked at it. but it did made me aware of many words.
and we also categories words in Hindi grammar language wise, so i came to know of the Portuguese and French words, as Hindi and Urdu grammar are almost equal, if not totally.
would try to supply with more.
merci = thanks in farsi ** **in french saaet = time in farsi in arabic
Thank you is actually "mamnoon" or "tashakur" in Farsi. The reason why merci is used is because of the French culture's influence over Iranians. Kinda like the British and India/Pakistan...A classic is also "sipaaz guzoram", meaning I'm grateful.
Tashakur is also used in Turkish.
Re: How to distinguish Arbi and Farsi words used in urdu ?
Tashakur is also Farsi but its used in Dari (Afghani Farsi) whereas the Iranians prefer using Merci. As for turkis i've heard that the word Urdu itself is Turkish is that true? Urdu has a few letters that are not in any of the languages of the middle east like dhaay (its like a ray but with a toi looking thing on it) I've tried ot have people pronounce that word and its virtually impossible for them, like saying Gari (car) the letter used in it is pretty unique to the languages of the subcontinent, including South Asian languages and those of Sri Lanka like Telegu and Tamil
Re: How to distinguish Arbi and Farsi words used in urdu ?
Isnt Sukriya a Farsi word? dont they use it then? or is it Arbi? cause i heard some Lebanese saying Sukran(which does sound close to Sukriya) as 'Thanks', and they speak Arabic.
and Telegu and Tamil are not the languages of Sri Lanka.
Re: How to distinguish Arbi and Farsi words used in urdu ?
European words in Urdu:
Portuguese(Portugali): Almirah, Istari, Kaptaan, Nilaam, Padri, Santara, Balti, Saabun, Aaya, Gamla, Chabi, Toliya, Mistari
French(Francici): Kaju, Kartus, Angrezi(evolved from how French used to say English)
these words came into the desi languages during the French and Portuguese period in the sub-continent.
and some got corrupted too.
the word Urdu came from the Turki word, Ordu, meaning Camp, as Urdu evolved in the camps of Mughal kings when soldiers of many languages and nationality mixed together and formed a common language.
Re: How to distinguish Arbi and Farsi words used in urdu ?
Tashakkur must have its origin from Arabic as Shaakir and Mashkoor is definitely Arabic
Re: How to distinguish Arbi and Farsi words used in urdu ?
Srilanka has two official languages Sinhala and Tamil although Telgu is also spoken in some parts. This well documented, I am not familiar with Sinhala but am with Tamil
Re: How to distinguish Arbi and Farsi words used in urdu ?
Tamil maybe one of the official languages of SL, but its place of origin lies in Tamil Nadu. and Telugu in SL?? you sure? the Tamils of Sri Lanka are migrants from Tamil Nadu. even the Sinhalas migrated from North India.