Mind the Till
File this under We Appreciate the Effort.
Writers constantly render the alternate form of until as ’til. (Half the time it’s with the wrong apostrophe—‘til—but we’ll leave that for another day.) But in a cruel twist brought to you by the mutative quality of the English language*, the proper form is till. That’s right, no apostrophe to denote that letters have been sheared off, and an extra l thrown in.
But don’t get discouraged! I like the way a writer thinks when she uses ’til. While it’s wrong, it does show that she recognizes that in many cases a shortened version of a word needs to use an apostrophe to show that letters are missing. Just not, for reasons I hope an etymologist will let us know, with till.
*Please note I am not endorsing descriptivism—or if I am, it’s a much slower version than certain elements among us might like to see.
The Writing Guide 
That is a weird little rule.
I’ve had till changed to ’til by well-meaning editors on several occasions. It’s an awkward but delicious feeling to say to a superior, “You know, strange as it may be, it actually IS till with a double L.” They always look it up and grudgingly compliment my knowledge of stupid minutiae.
I, too, would like to know how this word developed.