Tahm Kench's song; a Lore Question

So, this is just a curiosity I've had for the longest time now since Tahm's release and I've decided to finally ask on the boards about it. I asked a long time ago on the Q&A but never saw a reply so it's finally eaten away at me enough that I had to bring it up again XP. (Hehe, 'eaten away' )

Anyways, Tahm's song. It intrigues me honestly. It's his login theme, his dance emote, he hums it in his champion teaser video- Tahm quite clearly has ties with and enjoys this tune. Where does it come from though? Is it something Tahm has sung to himself for ages? Did he hear it once and decided he liked it? If so, where did he hear it from? Was the song associated with him before he knew about it and that's why he likes it so much? I am confuse.

What do you guys think? Thoughts, theories? I feel like it's an aspect of our favorite Two-faced Fish that's been heavily overlooked despite all the connections it could potentially have :)