Shorthands like “yd” for yard and “a/c” for air conditioning are pretty straightforward, but there are some misconceptions about others. For example, take “a.m.” and “p.m.” People in the U.S. are constantly thinking and talking about time in terms of a.m. and p.m., but if you ask someone what those letters stand for, you may be surprised how little people actually know about the abbreviations. Some say it’s “after midnight” or “past midday,” but that isn’t exactly true... In fact, like many words and phrases in the English language, a.m. is short for a Latin phrase, “ante meridiem” (or “before midday”), while p.m. is short for “post meridiem” (or “after midday”). During the Renaissance period, mechanical clocks with 12-hour analog dials appeared in churches and palaces throughout Europe.

Source: Huffington Post March 23, 2018 21:22 UTC