The word "为什么" is formed through the historical fusion and grammaticalization of three distinct characters: the character 为 (wèi), which originally meant "to do" or "for the purpose of"; the character 什 (shén), a shorthand or variant form related to "what" or "which"; and the character 么 (me), a later-added interrogative particle used to form questions. Over time, these components were combined and lexicalized into a single, fixed compound, where the original literal sense of "for what" or "doing what" condensed into the modern, unified meaning of "why".