Southern
Old English sūtherne (see south, -ern).
wiktionary
From Middle English southerne, sothern, sutherne, from Old English sūþerne(“southern, southerly, coming from the south; of southern make”), from Proto-Germanic *sunþrōnijaz(“southern”), from Proto-Indo-European*sh₂un-, *sh₂wen-, r/n-stem alternation of *sóh₂wl̥(“sun”). Cognate with Scots southron, sudron(“southern”), Old Frisian sūthern, sūdern(“southern”), Middle Low German sūdern(“southern”), Middle High German sundern(“southern”), Icelandic suðrænn(“southern, tropical”).
Morphologically south + -ern.
etymonline
southern
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 constellation Southern Cross so called in English by 1756.
