-ster

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. One that is associated with, participates in, makes, or does: songster.
2. n. One that is: youngster.

Century Dictionary and Cyclopedia

1. n. A termination denoting occupation, as in maltster, gamester, spinster, songster, etc. In the earliest times, and up to about the end of the thirteenth century, it was generally the sign of the feminine gender, corresponding to the masculine -ere or -er. In the fourteenth century it began to give place as a feminine termination to the Norman -ess, with which it was later often combined, as in seamstress, sempstress, songstress, or, if it survived, was used chiefly as masculine, and took on new meanings of contempt or depreciation, as in trickster, gamester, punster, etc., or indicated simple agency or existence, as in deemster, doomster, huckster, tapster, teamster, upholster, roadster, youngster, etc. Some of the older nouns with this suffix survive as surnames, as Baxter, Webster, Sangster, Dempster, etc.
2. n. An abbreviation of sterling.

Wiktionary

1. n. Someone who is, or who is associated with, or who does something specified.
2. n. humorous A diminutive appended to a person's name.

GNU Webster's 1913

1. A suffix denoting the agent (originally a woman), especially a person who does something with skill or as an occupation; as in spinster (originally, a woman who spins), songster, baxter (= bakester), youngster.