There are various rules about whether an adjective takes '-er/-est' or 'more/most', but they're based on syllable count and don't give an etymological rationale.

Does anyone know? Is it based on whether the word was Saxon in origin?

  • 2
    The rationale is what sounds best to the English ear, not word origin. The whole rule is that one syllable takes 'est,' three take 'most,' and for two, it depends on how it sounds (silkiest, most awkward). – Yosef Baskin Jun 9 '17 at 13:26
  • 1
    Rude is from Latin, and the superlative is rudest. New is from Old English, and the superlative is newest. Important is from Latin, and the superlative is most important. Outlandish is from Old English, and the superlative is most outlandish. The only superlatives that betray the word origin are the irregular ones: e.g. farther, best and worst. – Peter Shor Jun 9 '17 at 14:11
  • OP is asking about the origin, not the rule. – user66974 Jun 9 '17 at 14:11
  • 2
    If they're asking about the origin, then they need to edit it and specify that is what they are asking; the title makes people think they are asking about the rule. I will vote to reopen if the OP will edit the question to be more clear about that intent. – Hank Jun 9 '17 at 14:42
  • None of the simplistic “rules” for “knowing” whether to use an analytic form (typically with more or most) versus whether instead to use a synthetic one with ‑(e)r, ‑(e)st for the comparative and superlative degrees of adjectives and adverbs guarantees you will always correctly deduce acceptability if one or another form. There are certainly patterns to be observed, some more faint than others, but virtually none are dispositive. The duplicate to which this was closed still appears to be the same question as this one, but that duplicate has no expert answer, which will not be simple. – tchrist Jun 9 '17 at 15:32