best (adj.)youdaoicibaDictYouDict[best 词源字典]
Old English beste, reduced by assimilation of -t- from earlier Old English betst "best, first, in the best manner," originally superlative of bot "remedy, reparation," the root word now only surviving in to boot (see boot (n.2)), though its comparative, better, and superlative, best, have been transferred to good (and in some cases well). From Proto-Germanic root *bat-, with comparative *batizon and superlative *batistaz (cognates: Old Frisian, Old Saxon, Middle Dutch best, Old High German bezzist, German best, Old Norse beztr, Gothic batists).
The best-laid schemes o' mice an' men
Gang aft agley,
An' lea'e us nought but grief an' pain,
For promis'd joy!

[Burns]
Best-seller as short for "best-selling book" is from 1902, apparently originally in the publishing trade; best friend was in Chaucer (late 14c.). Best girl is first attested 1881, American English; best man is 1814, originally Scottish, replacing groomsman. To be able to do something with the best of them is recorded by 1748.[best etymology, best origin, 英语词源]
primal (adj.)youdaoicibaDictYouDict
c. 1600, "belonging to the earliest age," from Medieval Latin primalis "primary," from Latin primus "first" (see prime (adj.)). Psychological sense, in reference to Freud's theory of behaviors springing from the earliest stage of emotional development, is attested from 1918. Primal scream is from a best-selling book of 1971.