The term axé (also spelled aché or ashé – all pronounced ah-SHEH) comes from the Yoruba peoples of Western Africa. It is the name they gave to the life force; the concept is similar to the Eastern idea of qi.
In capoeira today, axé has come to mean something like “energy.” If a roda has a lot of axé, it means it has good vibes, powerful energy. Some groups use the word as a greeting.
Some references to axé in capoeira songs:
Axé, axé / Capoeira tem muito axé
Axé, axé / Capoeira has lots of axé
Dos velhos Mestres que viveram na Bahia,
Manda todo o seu axé e também sua magia
Bahia manda seu axé pra mim
From the old Mestres who lived in Bahia,
Send all your axé and also your magic
Bahia send your axé to me
Axé also refers to a style of popular music (not related to capoeira) that originated in Salvador, Bahia.
There is also a capoeira group called Axé Capoeira that was founded by Mestre Barrão.