Look up walkabout in Wiktionary, the free dictionary.
Walkabout refers to a rite of passage during which male Australian Aborigines would undergo a journey during adolescence and live in the wilderness for a period as long as six months.
In this practice they would trace the paths, or "songlines", that their ancestors took, and imitate, in a fashion, their heroic deeds. Merriam-Webster, however, identifies the noun as a 1908 coinage referring to "a short period of wandering bush life engaged in by an Australian Aborigine as an occasional interruption of regular work", with the only mention of "spiritual journey" coming in a usage example from a latter-day travel writer.
To white employers, this urge to depart without notice (and reappear just as suddenly) was seen as something inherent in the Aboriginal nature, but the reasons may be more mundane: workers who wanted or needed to attend a ceremony or visit relatives did not accept employers' control over such matters (especially since permission was generally hard to get).