also: いさらおがわ
noun
trickling brook
Archaic literary term for a small, gently flowing stream. Not used in modern everyday Japanese; encountered mainly in classical poetry or historical descriptions.
古い和歌に「いささ小川のせせらぎ」という表現が見られる。
In old waka poetry, one finds the phrase 'the murmur of a trickling brook'.
Modern common word for 'brook' or 'stream'; いささ小川 is an archaic, poetic variant emphasizing a trickling flow.
The prefix いささ (also いさら) is an old element meaning 'small' or 'fine', combined with 小川 (brook). The exact origin of いささ/いさら is uncertain, but it appears in several archaic compounds.