What is the meaning of the phrase "sow wild oats"? Where did it come from?
According to etymonline.com,
It is less clear when the meaning changed to its current one. That is, currently, to "sow wild oats" normally means (for a man) to have sex with as many women as possible. "Wild oats" here specifically means hypothetical unwanted offspring.
Here's a decent primer on the idiom: http://www.worldwidewords.org/qa/qa-sow1.htm
Wild oats are a weed whose seed looks a lot like certain cereal grains, and is thus hard to separate when sowing. Quoth the webpage:
So it's pretty much the same meaning as 1542, the first known usage, with perhaps a little more promiscuous sexual connotation these days.