Reader Erik Engstrom was surprised to see this misuse of the word leech in an article at Wired:
. . . certain chemicals that leech metals from the body.
Pronounced the same [lēch], leech and leach have different meanings.
The word leech is the old word for “doctor.” It comes from OE laece, “physician.” Leech meaning “bloodsucking aquatic worm” may have originally been a different word, but assimilated to the word for doctor, possibly because doctors used leeches for blood-letting.
Figuratively, a leech is a person in a parasitic relationship with another.
The word leach comes from the OE verb leccan, “to moisten.” In current usage the verb leach refers to percolation of a liquid. The Wired writer was using the word in the sense of “to take away by percolation.”
Related to leach is the word leak, “to let water in or out.” It may seem that the figurative sense of leak to mean “allowing secret matters come to public attention” must be a 20th century innovation, but it’s not.
The intransitive use of leak with this figurative meaning dates from 1832. The transitive use, “to leak information,” is recorded from 1859. The figurative use of the noun leak to mean “the information leaked” didn’t come along until 1950: The Post published the latest leak from the White House.
We can thank Henry Miller for the first published use of leak as a noun meaning “the act of urination” (Tropic of Cancer ).
Leak as a verb meaning “to piss,” however, dates from 1596.