Undersurface

Part of speech: noun

Definitions

1. The bottom or lower side of something, especially a surface that is not normally visible or exposed
2. The hidden lower side of an object that is typically not observable, found beneath the primary surface that is usually seen
3. The underside of an object or area that lies below the part commonly seen or touched

Etymology: "Undersurface" is about as transparent as English compounds get: the prefix "under-" joined to "surface." The prefix descends from Old English "under," which goes back through Proto-Germanic to a root shared with many European languages, and it has meant "beneath, below" for the whole of the word's recorded life in English. The second half came into English from Middle French "surface," itself borrowed from Latin roots meaning "over" and "face," so "surface" literally means "upon the face." Combining the two gives a plain sense of the face of something turned downward, the side resting on the ground or the lowest exposed layer. Because "surface" is an older borrowing, the compound is a later formation built on the existing English pieces rather than a word with its own separate history.

Synonyms: bottom, underpart