The previous post mentioned that Spanish and English borrowed lava from Italian, which may have acquired it from Latin lābēs ‘a fall,’ given the way lava “falls” down the side of a volcano. The Latin noun had come from the verb lābī, whose meanings included ‘to move gently along a smooth surface, to fall, slide; to slide, slip, or glide down, to fall down, to sink.’ From that verb came the adjective lābilis, meaning ‘slipping, gliding, prone to slip or slide,’ which Spanish and English have carried over as lábil/labile. The definitions given in the DRAE and the American Heritage Dictionary are, respectively:
1. Que resbala o se desliza fácilmente.
2. Frágil, caduco, débil.
3. Poco estable, poco firme en sus resoluciones.
4. Quím. Dicho de un compuesto: Inestable, que se transforma fácilmente en otro.
1. Open to change; readily changeable or unstable: labile chemical compounds; tissues with labile cell populations.
2. Fluctuating widely: labile hypertension; labile emotions.
3. Decomposing readily: the labile component of organic matter.
While you may be hard put to think of any other related words, once I point out that the past participle of Latin lābī was lāpsus, you should immediately think of lapso/lapse. (English can use lapse as a verb, but the DRAE doesn’t show a corresponding *lapsar or *lapsear.) In addition, both languages sometimes use the original Latin noun lāpsus, which may be best known in the phrase lāpsus linguae ‘a slip of the tongue.’ Less frequently seen phrases are lāpsus memoriae ‘a lapse of memory’ and, especially in the computer age, lāpsus calamī ‘a slip of the pen.’
© 2015 Steven Schwartzman