dander (n.1)

"scurf, dandruff," 1786; earlier dandro (1590s), of uncertain origin (see dandruff).

"temper, anger, passion," 1831, American English, of unknown origin; perhaps a figurative use somehow of dander (n.1), or of West Indian dander, dunder "fermentation of sugar" (in English from 1796), from Spanish redundar "to overflow," from Latin redundare (see redundant).