alpha n.

c. 1300, from Latin alpha, from Greek alpha, from Hebrew or Phoenician aleph (see aleph). The Greeks added -a because Greek words cannot end in most consonants.

The sense of "beginning" of anything is from late 14c., and in this it is often paired with omega (the last letter in the Greek alphabet, representing "the end"). The sense of "first in a sequence" is from 1620s. In astronomy, the designation of the brightest star of each constellation (the use of Greek letters in star names began with Bayer's atlas in 1603). Alpha male was in use by c. 1960 among scientists studying animals; applied to humans in society from c. 1992.