Blasphemy of the Divine name, so fearfully common in professedly Christian countries, is almost unknown to the African heathen. Though the native name for God, Anyambe, is improperly used in names of persons (which is not intended for disrespect), it is not often actually blasphemed. An equivalent blasphemy, is occasionally practised in the misuse of the name of their great and sacred spirit-society. In the Benga tribe "Saba?" and "Sabali?" used interrogatively, mean only "True?" "Is that so?"; but, used positively, they are of the nature of an oath, especially when the society's name (Ukuk) was added: "Saba n' Ukuku" (True! by Ukuk!).
On the Ogowe River, in the Galwa tribe, the name of that society was Isyoga, more commonly spoken of as Yasi. In the initiation into it the neophytes were taught a long and very solemn adjuration, that could be uttered only among the initiated, as an oath; but they were allowed commonly to use simply its title "Yasi," the utterance of that one word being accompanied by a downward sweep of the right hand over the left arm from shoulder to hand. It was not permitted to women to speak this word.
In no tribes with which I have lived was this "By-the-Spirit" oath used so much as among the Galwa of the Ogowe. It became monotonously frequent, in and out of season, in all conversations and on the slightest assertion or the simplest excitement.
I became very tired of "Yasi! Yasi! Yasi!" and that sweep of the right hand, for the doing of which the canoe paddle or a tool was laid down. And, by the way, the more of a liar a man was, the more frequent and vociferous was he in his persistent use of "By Yasi!"