sīde (Middle High German) comes from Old High German sīda, from Proto-Germanic *sīdā, from Latin sēta, from Latin saeta, from Proto-Italic saitā, from Proto-Indo-European séh₂ito-, from Proto-Indo-European sh₂ey-, from Proto-Indo-European seh₂- — to satiate, satisfy.
Ancestry of “sīde”, step by step
sīde traces back through two separate lines of ancestry.