aurora borealis (n.)youdaoicibaDictYouDict
1620s, "Northern Lights," literally "northern dawn," said to have been coined by French philosopher Petrus Gassendus (1592-1655) after a spectacular display seen in France Sept. 2, 1621; see aurora + boreal. In northern Scotland and among sailors, sometimes called the dancers or the merry dancers.
northern (adj.)youdaoicibaDictYouDict
Old English norþerna, norðerne "northern, Northumbrian, Scandinavian," cognate with Old High German nordroni, Old Norse norroenn (see north). With -erne, suffix denoting direction. Related: Northernmost. Northerner in U.S. geo-political sense is attested from 1831. Northern lights "aurora borealis" first recorded by that name 1721 (earlier north-light, 1706).
petty (adj.)youdaoicibaDictYouDict
late 14c., "small," from phonemic spelling of Old French petit "small" (see petit). In English, not originally disparaging (as still in petty cash, 1834; petty officer, 1570s). Meaning "of small importance" is recorded from 1520s; that of "small-minded" is from 1580s. Related: Pettily; pettiness. An old name for "Northern Lights" was petty dancers.