Are 新しい and 新たに etymologically related?

Question

The words 新しい{あたらしい} and 新た{あらた}に sound very similar to me, but I wonder whether they are really related. If so the root must have undergone metathesis (switching the order of sounds). Are they actually etymologically related?

Note: I saw this question but I'm asking about etymology rather than usage. (Though there does happen to be some relevant information in the answer there.)

Answer 1

One theory is indeed that 新しい derives from あらたし via metathesis as あらたし in the beginning of the Heian period became あたらし and then あたらしい.

語源由来辞典 lists another theory: あらたし (meaning "new") was confused with the already existing あたらし meaning 惜しい. あたらし was used with the meaning "new" and the other meaning of 惜しい fell largely out of use.

In any case, 新しい and 新た are etymologically related.

Answer 2

For new, there are several old words that we can find, poking around in Shogakukan's 国語大辞典:

• 新{あら}た
  From Old Japanese, appearing in the 万{まん}葉{よう}集{しゅう} poetry compilation, dating to roughly 759.
  Derived from 生{あ}る "to come into being" (same stem as for 現{あらわ}れる "to become manifest, to appear") + た as a suffixing element indicating state, probably related to the た still used in modern Japanese to indicate completion and past tense.
  Probably cognate with 荒{あら} "rough".
• 新{あらた}し
  Appears in the Early Middle Japanese of the Heian period.
  Derived from older 新{あら}た + adjectivizing suffix し.
• 新{あたら}し
  Appears in the Early Middle Japanese of the Heian period.
  Shogakukan explains that Middle Japanese saw both aratashi and atarashi used to mean "new". As Earthliŋ notes, this was probably a shift in pronunciation from aratashi, with the metathesis (reversal of the ra and ta sounds) influenced by Old Japanese-derived adjective 惜{あたら} or 可惜{あたら} and its derived forms 惜{あたら}し or 可惜{あたら}し, itself cognate with 値{あたい} "value, worth" and 当{あ}たる / 当{あ}てる, from ancient root form atu. Over time, 惜{あたら}し "wonderful, valuable, precious" fell out of use, and atarashi became the standard reading for the "new" sense instead.