The tags influences (23 questions) and inspiration (26 questions) both seem to have roughly the same meaning: they're both for questions about where an SF/F author's ideas came from, what influenced or inspired them to write the things they did. Examples:
Shall we synonymise and merge these tags?
They also bear some similarity to the origins tag (now synonymised with the history-of tag), but I think the latter is different enough not to be synonymised: it's more about the history of the genre as a whole, e.g. "where did X first appear in science fiction literature?", whereas the influences/inspiration tags are more about the history of a specific idea, e.g. "where did author X get this idea?" (Admittedly the tag wikis should be edited to make this clear [hint hint] ...)
Note: PLEASE DO NOT start editing the tags on these questions manually before a consensus is reached here. The community has expressed their disapproval of multiple tag edits cluttering up the front page, and it's entirely unnecessary in this case: if we do agree to merge these tags, we can do the retagging automatically without bumping any questions at all.