Origin: Germanic Old English prefix
Overly has 3 different meanings across 1 category:
Superficial; not thorough; careless, negligent, inattentive.
"The inspector's overly casual review of the safety reports failed to catch several critical flaws."
In plain English: Overly means something is done to an excessive degree, often making it more than necessary or appropriate.
"The cake was overly sweet and difficult to eat."
To an excessive degree.
"The teacher scolded the student overly harshly for a minor mistake."
Overly is formed by combining the word over with the adverbial suffix -ly. This construction simply adds a "-like" or "in an excessive manner" quality to the base word.