Etymology: < French compas (12th cent. in Littré) ‘measure, pair of compasses, circle’; in modern French also ‘mariner's compass’; = Provençal compas, Spanish compas ‘pair of compasses, measure, rule of life, pattern’, Portuguese compasso ‘pair of compasses’, Italian compasso ‘a compasse, a round, also a paire of compasses’ (Florio); medieval Latin compassus = circinus pair of compasses (Du Cange). Compare also German compass, kompass, mariner's compass, formerly also gnomon, sun-dial, portable dial, Dutch kompas, Swedish compass, kompass, Danish compas, Norwegian kompas, (all) mariner's compass. (This is the exclusive sense in the Germanic languages, as ‘pair of compasses’ is predominant in the Romanic.) The history of this word and its associated verb in the Romanic languages has not yet been determined, and it presents many points of uncertainty. It is doubtful whether the noun is Common Romanic (the Spanish being apparently < French or Provençal), and as yet uncertain whether the noun is derived from the verb, or the verb from the noun. If the noun was the origin, it would predicate a Latin type *compassus, < com- together or intensive + ? passus step, pace; if the verb was the earlier, compassare would be ‘to pass or step together’ or ‘completely’ (see Diez passare), and *compassus, compasso, the action of doing so. The early history of the senses of the noun is equally obscure: in Old French, ‘measure’, primarily perhaps ‘measure kept in walking together’, ‘artifice, subtilty’, and ‘pair of compasses’, appear all to be early senses; it is at present impossible to say whether the instrument took its name from ‘measuring’ or from ‘equal stepping’. It is probable that the sense ‘circumference, circle, round’ which is slightly exemplified in Old French, but has received so great a development in English, is derived from the name of the instrument; but the converse is also possible; compare Latin circinus compasses, < circa round, etc.; also German zirkel, (1) circle, (2) compasses. The later application to the Mariner's Compass, recognized in modern French, but chiefly developed in English and the Germanic languages, is also of obscure origin; it may easily have arisen out of the sense ‘circle’ or ‘circuit’, as showing the circle of the winds; but in German this sense appears to have been preceded by those of ‘gnomon’ and ‘sun-dial’, which may point in another direction. The Greek name of the circinus or compasses was διαβήτης, < διαβαίνειν to stride or walk with the legs apart, to stride, step, or pass over: it is not impossible that compassus and compassare may have been employed to render these words, and as διαβήτης also meant the gnomon of a sun-dial, it is conceivable that this indicates the way in which compassus came to be used for dial, and mariner's compass. The Old French senses all appear early in Middle English In the uncertainty as to the relations between these, it is impossible to arrange them in any certain order in English, and that adopted is merely provisional, and subject to alteration when Romanic scholars shall have ascertained the previous history of the word in their own domain.

Etymology: Alteration of compost n.¹

Etymology: < French compasse-r (12th cent. in Littré), to measure, design, contrive, regulate, adjust; compare Provençal compasar, Spanish compasar ‘to measure with a compass, to compass about’ (Minsheu), Italian compassare to measure with compasses, to weigh in the mind, ‘to compasse about’ (Florio) < Latin type *compassāre. See the n.

Etymology: see compass n.²