Socks were fabric garments for covering the feet.
Prior to departing from the planet where Q'ell lived, Charles Tucker gave the young boy a parting gift, a PADD containing the schematics for the Enterprise, adding, "you said you like to look at starships. This one'll knock your socks off." (ENT: "Marauders")
During bachelorhood, Miles O'Brien had the habit of always leaving his socks on the floor of his quarters every night, as his wife Keiko had explained to Data and Jenna D'Sora in 2367. When Miles and Keiko got married, she made the mistake of picking his socks up a few times, but eventually came to the realization that if she kept it up she would doing it for he rest of her life, so she stopped, figuring that Miles would get the message and do it himself. Ten days later, the sock pile stood half a meter high, and after two weeks, she couldn't stand it anymore and she bundled them up and put them in the cleaning processor, and had continued to do it to that day. While Miles denied the socks were ever piled that high, he did say that she did a very good job at taking care of his socks. (TNG: "In Theory")