Because I was curious, Dr Q

[montjoye]

Wan´kle

a.

1.

Not to be depended on; weak; unstabl

sark

"shirt," late O.E. serc, surviving as a Scottish and northern dialect word, from O.N. serkr, cognate with O.E. serk (see berserk). Cf. also Lith. sarkas "shirt," O.C.S. sraka "tunic," Rus. sorocka, Finn. sarkki "shirt," which are perhaps from Gmc.

 

so "Wankle as a wet sark" translates roughly to "Limp as a wet shirt"