Etymology of "shagged [out]" (BrE exhausted, knackered)

Question

I was intrigued by this comment to an earlier ELU post...

[shagged out] Meaning 'very tired', presumably originating from having lots of sex but used generally to mean tired for whatever reason

...which led me to this dictionary.com entry...

shagged [shagd] adjective Informal
weary; exhausted (usually followed by out)
They were completely shagged out from the long trip.
Origin: 1930–35; origin uncertain

OED tells me the coarse BrE slang verb to shag is also "origin uncertain" (perhaps relating to a rare/obsolete verb sense shag=toss about).

Does anyone know anything more about this? Was that ELU commenter on the right track?

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EDIT: Just to clarify. Effectively, I'm asking two questions:

1: Are shagged=tired and shag=fuck cognate? (do they have a common origin?)
2: If so, does that mean the commenter was right (i.e. - shagged=tired originally implied post-coital)?

Answer 1

The copulation sense of shag certainly seems to have come first, so to speak. From Francis Grose, A Classical Dictionary of the Vulgar Tongue, Third Edition (1796):

TO SHAG. To copulate. He is but bad shag; he is no able woman's man.

Eric Partridge, A Dictionary of Slang and Unconventional English, Fifth Edition (1961) sees the same possible connection that you do:

shag, v.t. To coit (with a woman) : late C. 18–20. Very gen. among soldiers in G.W. Grose, 2nd ed. Prob. ex [obsolete] shag, to shake,toss about. ...2. Whence, perhaps, v.i., to masturbate : Public Schools : certainly ca. 1900 and prob. many years earlier.

shag, adj. Exhausted, esp. after games : Marlborough College : C. 20. Perhaps ex shag, v., 2, q.v. (A thin and weedy dog that, ca. 1919–23, haunted the college precincts, was known as Shagpak or Shaghat, as Mr. A.B.R. Fairclough, formerly of the Alcuin Press, tells me.)

Interestingly, Partridge also has an entry for "wet as a shag" (from circa 1830), meaning "very wet indeed," in reference to the cormorant (or shag), whose feathers lack the oil that many swimming birds possess and thus get very wet indeed. This also explains the cormorant's habit of standing on a dock, rock, or tree branch with its wings motionlessly outstretched, to dry its feathers. I'm a bit surprised that Partridge didn't entertain the possibility that the exhausted sense of shagged might derive from the bird's motionless torpor at such times, following a vigorous session of fish catching.

John Ayto & John Simpson, The Oxford Dictionary of Modern Slang (1992) takes a view shag and shagged that is similar to Partridge's:

shag (1) coarse. verb trans and intr. 1 To have sex (with) 1788– ... 2 Used in curses and exclamations 1933– ... 3 An act of copulation. 1937– 4 One who copulates; used as a general term of abuse. 1971– ... [Origin uncertain; perh. from obs. shag to shake, waggle.]

...

shagged adjective Weary, exhausted; often followed by out. 1932– ...{Origin uncertain; perh. related to SHAG (1) verb.]

Ayto & Simpson also notes the existence of a verb shag from 1851 meaning "to wander aimlessly; to traipse; to go away." That term's origin is unknown.

Answer 2

It appears that the verb to shag has both origin ' copulate' and current slang meaning related to sex;

Shag: etymology

• "copulate with," 1788, probably from obsolete verb shag (late 14c.) "to shake, waggle," which probably is connected to shake (v.).

Shag:

• v. shagged, shag·ging, shags Chiefly British Vulgar Slang.

• v.tr. To engage in sexual intercourse with. v.intr. To engage in sexual intercourse. [Perhaps from obsolete shag, to shake, wiggle.]

Answer 3

When I was at school in the 1960s and forced to go on cross-country runs, my PE teacher used to insist we used a running style called shagging.

This caused a certain amount of schoolboy amusement due to the other use of the word. Shagging was a running style which used less energy over a long run. It would be known to most people as jogging. This would explain exhaustion.

I have never heard shagging used this way by anyone else. It may be a dialect word. The teacher in question was from South Wales but the Welsh language can't be blamed for this use of shagging.