Meaning

verb weaken the consistency of (a chemical substance)

verb become weaker, in strength, value, or magnitude

adjective reduced in strength

originThe verb is first attested in 1530, the adjective in 1626; borrowed from Latin attenuātus, the perfect passive participle of attenuō (see -ate (verb-forming suffix) and -ate (adjective-forming suffix)), from ad- (“to, towards, at”) + tenuo (“to make thin”), itself from tenuis (“thin”) + -ō (verb-forming suffix).

Etymology from Wiktionary, CC BY-SA 3.0