That simply doesn’t reflect the history of the words. Till has been considered a perfectly good preposition in general English since about 1300. It first appeared in northern varieties of Old English around 800. Until, by contrast, is etymologically a compound of und + till, and it was often written untill. It came into use about 400 years after till.
Beginning in the 20th century, until started becoming more frequent in use than its synonym till—so much so that people, perhaps especially those who didn’t read much, started thinking that ’til is really an informal contraction, as opposed to the perfectly good, normal word till. Soon advertisers got it wrong, and the little virus spread. Among the literati, the supposed contraction ’til became a badge of illiteracy.
Usage writers have long warned against ’til:
• “Either till or until, but not ’til.”—John B. Bremner, Words on Words 373 (1980).
• “Till is not a clipped version of until: both are Standard words. Until may be considered a trifle more Formal, but both occur at all levels. ’Til is a variant spelling used by those who think (incorrectly) that till is a clipped form. At best it looks old-fashioned and self-conscious. Use till instead.” —Kenneth G. Wilson, The Columbia Guide to Standard American English 438 (1993).
• “’til. Do not use except in quoting a written or printed source. But till is largely interchangeable with until.”—Allan M. Siegal & William G. Connolly, The New York Times Manual of Style and Usage 331 (1999).
• “Till or until. But not ’til.” —The Associated Press Stylebook and Briefing on Media Law 267 (2013).
Two last things. First, even worse is ’till, which sometimes appeared in the 18th century and before but has long been considered nonstandard. Second, please banish the thought that till is less formal than until. Not so. The prepositional till has appeared in heightened prose and poetry throughout the history of English.
As with so many other word choices, euphony governs whether to use till or until. So use either one—but never ’til—while waiting for the cows to come home.
Garner’s Dictionary of Legal Usage 894-95 (3d ed. 2011).
Garner’s Modern American Usage 814 (3d ed. 2009).
Bryan A. Garner, President of LawProse Inc., is the most prolific CLE presenter in the U.S., having trained more than 150,000 lawyers and judges. His book — most prominently Black’s Law Dictionary and Garner’s Modern American Usage — have been cited as authority by every state and federal appellate court, including the highest. For more about him, go to www.lawprose.org. To follow him on Twitter: @bryanagarner.