Meaning of word Wahe Guru (vaha guru) as Explained by Bhai Gurdasa ji

The meaning of word vaha guru is well put forth by Bhai Gurdasa ji who is a contemporary of the fifth Sikh guru Arjun Dev ji. He is the one who penned down the Granth Sahib while the fifth guru recited it. Bhai Gurdasa has authored a book called ‘Vaara’ where he elaborates on the compilation of the mantra vaha guru.
In his book in the section of 1 Varaa, Pauri 49 he says:

Satyuga satgur vasdev va-va vishna nama japavey
duapara satgur hari krishna ha ha hari hari nama japavey
trete satgur rama jii ra ra rama jape such pavey
kaliyuga nanak gur govinda ga ga govinda nama alavey
care yagi cahu yugi panchin vic jai samavey
caro akshara ik kar vahaguru jap mantara japavey
Jaha te upjia phir taha samavey

Translation: In Satyayuga to attain the Lord, meditation on the Vasudeva form is advocated. The letter ‘v’ of vaha guru reminds of Vishnu. In Dvapara yuga Hari Krishna appeared; the letter ‘h’ of vaha guru reminds of Hari. In Treta yuga Rama appeared; the letter ‘r’ of vaha guru reminds of Rama. In Kali yuga came Nanak as a guru to make others chant Govinda. The letter ‘g’ of vaha guru reminds of Govinda. Thus the four yugas have concluded this. The four letters combined together to form this mantra (vaha guru) By chanting this mantra the living entity goes back from where he has come.