impassible adj.

word-forming element meaning "not, opposite of, without" (also im-, il-, ir- by assimilation of -n- with following consonant, a tendency which began in later Latin), from Latin in- "not," cognate with Greek an-, Old English un-, all from PIE root *ne- "not."

In Old French and Middle English often en-, but most of these forms have not survived in Modern English, and the few that do (enemy, for instance) no longer are felt as negative. The rule of thumb in English has been to use in- with obviously Latin elements, un- with native or nativized ones.

c. 1200, "the sufferings of Christ on the Cross; the death of Christ," from Old French passion "Christ's passion, physical suffering" (10c.), from Late Latin passionem (nominative passio) "suffering, enduring," from past-participle stem of Latin pati "to endure, undergo, experience," a word of uncertain origin. The notion is "that which must be endured."

The sense was extended to the sufferings of martyrs, and suffering and pain generally, by early 13c. It replaced Old English þolung (used in glosses to render Latin passio), literally "suffering," from þolian (v.) "to endure." In Middle English also sometimes "the state of being affected or acted upon by something external" (late 14c., compare passive).

In Middle English also "an ailment, disease, affliction;" also "an emotion, desire, inclination, feeling; desire to sin considered as an affliction" (mid-13c.). The specific meaning "intense or vehement emotion or desire" is attested from late 14c., from Late Latin use of passio to render Greek pathos "suffering," also "feeling, emotion." The specific sense of "sexual love" is attested by 1580s, but the word has been used of any lasting, controlling emotion (zeal; grief, sorrow; rage, anger; hope, joy). The meaning "strong liking, enthusiasm, predilection" is from 1630s; that of "object of great admiration or desire" is by 1732.

As compared with affection, the distinctive mark of passion is that it masters the mind, so that the person becomes seemingly its subject or its passive instrument, while an affection, though moving, affecting, or influencing one, still leaves him his self-control. The secondary meanings of the two words keep this difference. [Century Dictionary]

A passion-play (1843, in a German context) represents the scenes in the Passion of Christ. The passion-flower was so called from the 1630s.

The name passionflower — flos passionis — arose from the supposed resemblance of the corona to the crown of thorns, and of the other parts of the flower to the nails, or wounds, while the five sepals and five petals were taken to symbolize the ten apostles — Peter ... and Judas ... being left out of the reckoning. [Encyclopaedia Britannica, 1885]