mid-15c. (implied in smelter), from Dutch or Low German smelten, from Proto-Germanic *smelt- (source also of Old High German smelzan, German schmelzen "to melt"), from PIE *smeld-, variant of PIE root *mel- (1) "soft." Thus the word is related to melt (v.). Related: Smelted; smelting.
<a href="https://www.etymonline.com/word/smelter">Etymology of smelter by etymonline</a>
Harper, D. (n.d.). Etymology of smelter. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/smelter