"Professional courtesy! Heh-heh-heh!"

--end of a lousy lawyer joke.

For lawyer-shark, OED has 1806 and notes that it is a nautical term.

This is from the Sporting Magazine (London), October 1793, pg. 50:

A _water-lawyer_, or, in plainer terms, a _shark_, was caught last month

near Washington, by Mr. Richard Graham, tacksman of the fishery of J. C.

Curwen, Esq. It was included in a stake-net, with several salmon, which, as

supposed, it was in pursuit of Mr. Graham, and his servant had a severe

conflict with the voracious fish, in which a very string spear was shivered to

pieces. It was ten feet long.