shag (n.) Look up shag at Dictionary.com
1590s, "cloth having a velvet nap on one side," perhaps from Old English sceacga "rough matted hair or wool," from Proto-Germanic *skagjan (cognates: Old Norse skegg, Swedish skägg "beard"), perhaps related to Old High German scahho "promontory," Old Norse skagi "a cape, headland," with a connecting sense of "jutting out, projecting." But the word appears to be missing in Middle English. Of tobacco, "cut in fine shreds," it is recorded from 1789; of carpets, rugs, etc., from 1946.
shag (v.1) Look up shag at Dictionary.com
"copulate with," 1788, probably from obsolete verb shag (late 14c.) "to shake, waggle," which probably is connected to shake (v.).
And þe boot, amydde þe water, was shaggid. [Wyclif]
Compare shake it in U.S. blues slang from 1920s, ostensibly with reference to dancing. But compare shag (v.), used from 1610s in a sense "to roughen or make shaggy." Also the name of a dance popular in U.S. 1930s and '40s. Related: Shagged; shagging.
shag (v.2) Look up shag at Dictionary.com
in baseball, "to go after and catch" (fly balls), by 1913, of uncertain origin. Century Dictionary has it as a secondary sense of a shag (v.) "to rove about as a stroller or beggar" (1851), which is perhaps from shack (n.) "disreputable fellow" (1680s), short for shake-rag, an old term for a beggar.