Throughly is a typographical error for thoroughly–except when it’s not. According to the Oxford English Dictionary, the archaic form “throughly” dates to the mid-15th century and can mean “fully,” “completely,” or “perfectly,” as well as “through” and “throughout.” The word appears in early editions of Shakespeare’s The Merchant of Venice, when fair Portia is heard to say, “I am enformed throughly of the cause, Which is the Merchant here? and which the Jew?” It also appears in English translations of the Miserere (Psalm 50 (Vulgate)), often set to music:
Have mercy upon me, O God, after Thy great goodness: according to the multitude of Thy mercies do away mine offences.
Wash me throughly from my wickedness: and cleanse me from my sin.
Generally, the presence of the low-probability typo throughly should be questioned for items published after 1800. There are currently 24 such instances in the OhioLink catalog. However, a number of these actually represent republications of earlier materials or scores and recordings of “Wash Me Throughly.” So use care when making corrections in your own catalog!
(Thomas Sully’s Portia and Shylock, from Wikimedia Commons)