"statement in passing," a judge's expression of opinion not regarded as binding or decisive, Latin, literally "something said incidentally;" from obiter "by the way" + dictum in the legal sense "a judge's expression of opinion which is not the formal resolution of a case or determination of the court."
Obiter dicta, legal dicta ... uttered by the way (obiter), not upon the point or question pending, as if turning aside for the time from the main topic of the case to collateral subjects. [Century Dictionary]
Latin obiter is from ob "in front of, toward" (see ob-) + iter "journey" (from PIE root *ei- "to go"). Klein's sources, however, say it is ob with the suffix -iter on analogy of circiter "about" from circa. Also see obituary.