Here it is: 'til is NOT a word, it is "considered a spelling error". The words, interchangeably used, are till or until.
This is what Miriam Webster has to say:
till (til) 1. up to the time of; until: to fight till death 2. before (used in negative constructions): They didn't come till today. 3. before, to: My watch says ten till four. ... Usage. TILL and UNTIL are both very old in the language and are interchangeable as both prepositions and conjunctions. ... TILL is not a shortened form of UNTIL and is not spelled 'TILL. 'TIL is usually considered a spelling error, though commonly used in business and advertising: Open 'til ten.
My deepest and most sincere apologies to anyone who has been victim to my ignorance!
Write on my friends, but do not write "'til".