Origin: Germanic Old English prefix
Underlay has 6 different meanings across 2 categories:
a pad placed under a carpet
A layer (of earth, etc.) that lies under another; substratum.
raise or support (the level of printing) by inserting a piece of paper or cardboard under the type
"underlay the plate"
simple past tense of underlie
The word "underlay" comes from Middle English and Old English, originally meaning to place something underneath to support or prop it up. It is formed by combining the prefix "under-" with the verb "lay.