Having long, lank sides.

1

[1809.  My grandfather, when a very little boy tending pigs, having been kidnapped and severely flogged by a long sided Connecticut schoolmaster.—W. Irving, ‘A History of New-York,’ (1812), ii. 28].

2

[1809.  At the tail of these carts would stalk a crew of long limbed, lank sided varlets, with axes on their shoulders and packs on their backs, resolutely bent upon improving the country in despite of its proprietors.—Id., ii. 170.]

3

1817.  He was what is usually called a tall slabsided Virginian.—James K. Paulding, ‘Letters from the South,’ ii. 122 (N.Y.).

4

1823.  A large slabsided negro girl.—Mass. Spy, Oct. 22.

5

1825.  “Hold in! hold in! or you’re jam up, I swar!” cried out a long, slab-sided Virginian, as our adventurers went, staving through Broadway, in Mr. Ashley’s go-cart.—John Neal, ‘Brother Jonathan,’ ii. 303.

6

1848.  A brace of legs, thrust considerably too far through a pair of mottled pants, and attached to a couple of the largest-sized feet, which were encased in twin cowhide brogans, formed the underpinning to a long, slabsided body, of otherwise generous proportions.—Durivage and Burnham, ‘Stray Subjects,’ p. 102.

7

1848.  A long-legged, slab-sided specimen of humanity entered the cell.—W. E. Burton, ‘Waggeries,’ p. 169 (Phila.).

8

1852.  [He] observed in the seat before him a lean, slab-sided Yankee, every feature of whose face seemed to ask a question.—Knick. Mag., xxxix. 283 (March).

9

1856.  The Massachusetts man will tell you that the real slab-sided whittler is indigenous to Varmount and New-Hampshire, from the mountains of which he descends like a wolf on the fold to prey amid the fertile fields which lie green before him.—Id., xlvii. 267 (March).

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1867.  

        You did n’ chance to run ag’inst my son,
A long, slab-sided youngster with a gun?
Lowell, ‘Fitz-Adam’s Story’: Atlantic Monthly, Jan.    

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