"vaulted recess," 1670s, from French alcôve (17c.), from Spanish alcoba, from Arabic al-qobbah "the vaulted chamber," from Semitic base q-b-b "to be bent, crooked, vaulted." The al- is the Arabic definite article, "the."
alchemy
alcohol
alcoholic
alcoholism
Alcoran
alcove
Alcyone
Aldebaran
aldehyde
alder
alderman