What does "Non Non Biyori" mean?
While there's no official statement from the author, it's possibly a combination of nonbiri (のんびり, carefree) and hiyori* (ひより, 日和, fine weather), which can be interpreted as &quot;fine weather (or fine days) to be carefree.&quot;
This is strengthened by the fact that:

Outside of the manga/anime, there was also 「のんびりくえすと！」(Nonbiri Quest!) radio corner
The ending theme was 「のんのん日和」 (&quot;Non Non Biyori&quot;; here, hiyori is read as biyori due to rendaku/sequential voicing)


From the lyric of the ending theme,

のんびりと歌うから　のんきな風が吹いた
nonbiri to utau kara　nonki na kaze ga fuita

it might even imply that Non Non Biyori is a combination of nonki (easygoing), nonbiri, and (h/b)iyori.