In reality, the malevolent river spirit usurped Tahm Kench from the gambler:
Tahm is coincidentally homographic with Persian تهم tahm "swift > strong > bold"
Kench resembles two Middle English words:
one for "loud laughter" (from Old English canc, related to OE. cincian, > Engl. kink),
the other for "the deep bin in which animal skins and fish are salted," (variants: canch, kinch), maybe from Old English canne (> Engl. can) plus diminutive suffix -oc (cf. bullock).
Before Tahm Kench's release his laughter could be heard if a champion in turn laughed while standing in Summoner's Rift's river (only once per match and only by the champion laughing)
Tahm Kench was in production for seven months, time during which he was called 'Fish Tank', 'Fez Tank', and 'Twocoats'.
Tahm Kench's dance has him play the tune he hums in 'The River King' with his tongue (Rift Scuttler will join him if he dances near her)
Tahm Kench represents the foibles of mankind, an individual's inner flaws. His name and appearance change from culture to culture, person to person (his current name and form come from a Bilgewater gambler. He has no real name, no form of his own, only those he takes.
Tahm Kench's names, like Aatrox's battles, have been carved into Runeterran history but he, unlike the Darkin Blade, is too much of a gentleman to make a fuss about it.
Tahm Kench refers to himself as a "monstrous siren ", referencing chimeric songstresses who sweetly and sorrowfully lulled sailors into underwater dangers, just like Tahm Kench who deceptively brought desperados to short-term pleasantries but would utterly ruin their lives afterwards.
Tahm can eat whatever he wants, but his specific appetites are only sated when he strikes a bargain.
In some respects, Tahm Kench's preferred 'seasoning' methods resembles Stephen King's cosmic predator It, which preferred its victims' body "salted" with "chemicals of fear".
Tahm Kench has a unique taunts for 48 champions, the most out of any champion in the game.
Tahm Kench knows a lot of champions (both as fellows and adversaries, those who get consumed by their inner demons, and those who overcome them) and all Yordles have encountered him at various times (easily to manipulate when socially outcast, harder when not so)
He seems to be on friendly terms with, or at least respect, Aatrox (Tahm Kench calls him 'brother') given both manipulate mankind (their foibles and their lust for bloodshed, respectively) for personal gain as well as both being timeless entities known across the ages in various names and forms.
Tahm Kench is considered both an equal and a rival by Evelynn, as they are both long-lived demons that feed on human emotion for sustenance, with Tahm Kench preying on greed and the misery of loss, while Evelynn preys on lust and the pain she causes her victims.