Soften comes from soft + -en. Soft derives from Old English sōfte, sēfte ('gentle, mild, agreeable'), from Proto-Germanic *samftijaz ('level, even, gentle'). The historical chain includes Old English sōfte and Proto-Germanic *samftijaz. The quoted older senses, "gentle, mild, agreeable" and "level, even, gentle", supply the semantic anchors for soften. The formation is best read as suffixal and borrowed: the word soften carries its older form-history into a compact English lexical shape. In present English it is used as a verb, "to make or become softer, gentler, or less severe". English derivatives include softener and softening; related English forms include soft. The result is a verb whose etymology preserves both the older form and the later English specialization.