ぶらんこ

Etymology
Almost certainly from mimetic adverb. Compare, from adverb +.

The oldest attestation listed in the  is from 1867, but the word apparently became common earlier in the. This form appears to have superseded older in everyday use, first cited to 1685.

Often mentioned as possibly from. However, the →  vowel shift cannot be accounted for, nor can the difference between the  in Portuguese versus the hard  in Japanese. Considering also that the core adverbial root is attestable already in 1477 in the forms  and,  and older root  in 1221 in the form , well before  in 1542, any derivation directly from Portuguese is likely only a folk etymology.

Noun

 * 1)  a swing, a swingset
 * 2)   swinging, something that swings, particularly a hanged person