"most southerly, farthest toward the south," 1725, from southern + -most. Earlier was southermost (1550s); the older word was southmost.
Entries linking to southernmost
southern adj.
"of, pertaining to, directed toward, or coming from the south," Middle English southerne, from Old English suðerne, from suð "south" (see south) + -erne, suffix denoting direction. A common Germanic compound (Old Frisian suthern, Old Norse suðroenn, Old High German sundroni).
The southern-hemisphere constellation known as the Southern Cross was so called in English by 1756. Southern-fried as a generic reference to ways of cooking, etc. characteristic of the U.S. South is by 1972. Related: Southernism.
-most
superlative suffix of adjectives and adverbs, Middle English alteration (by influence of unrelated most) of Old English -mest, a double superlative, from -mo, -ma (cognate with Latin -mus; compare Old English forma "first," meduma "midmost") + superlative ending -est. Now generally mistaken as a suffixal form of most.