A chicken an egg question

I used to shag fly balls at baseball practice, but Coach caught me and made me let the flies go.

To make a long or rough nap or pile on (a cloth or other material). Obs. rare.

1671 E. BLOOD in Abridgm. Specif. Patents, Weaving (1861) 1 A rich silk shagg..made of a silke wast..and shagged by tezell or rowing cardes, like as English bayes, rowed fustians, or dimatyes.

Shag is first recorded in the late eighteenth century, in the second edition of Captain Francis Grose's Classical Dictionary of the Vulgar Tongue, defined as "to copulate." Through the nineteenth century, the word was apparently considered quite vulgar; it is only found in underground or privately printed books (such as Pearl, a pornographic newsletter published in 1879 and 1880). However there are several American examples during this period. Shag is said to have been common in the speech of British soldiers in World War One, where it may have been further exposed to Americans. It isn't until the post-WWII period, though, that it begins to appear openly in general writings. It is found only rarely in American use, and those few examples may be deliberate attempts at using a Briticism.

Shag has some standard derived forms--as a noun meaning 'an act of copulation' or 'a person considered as a sexual partner', and the like--and is also used in various phrases corresponding to other sexual verbs (shag off, shag you, etc.).

The origin of shag is unfortunately unknown. There is an earlier verb shag meaning 'to shake; waggle', which fits perfectly semantically (compare frig, which originally meant 'to move back and forth' and then developed senses like 'to masturbate', 'to copulate', etc.), but this word was apparently never very common and no examples are known after the sixteenth century. Still, it is the most likely candidate. The later verb shag 'to chase', used especially in baseball, is also of unknown origin and its relationship to our shag is unknown.

shag (v.)
"copulate with," 1788, probably from obs. verb shag (c.1380) "to shake, waggle," which probably is connected to shake (cf. shake, shake it in U.S. blues slang from 1920s, ostensibly with ref. to dancing).
"And þe boot, amydde þe water, was shaggid." [Wyclif]
Also the name of a dance popular in U.S. 1930s and '40s. The baseball verb meaning "to catch" (fly balls) is attested from 1913, of uncertain origin or connection to other senses of the word.

So, me and littlek were driving up to New Hampshire....