Learning Words via Etymologies

I'm using FlashcardDB to study Spanish vocabulary. Generally it's going pretty well, but some similar words are really tripping me up; I can't keep them straight! So, to help myself, I've researched the etymologies of the Spanish words and tried to find cognates, however distant, in English.

This works like silly mnemonics, except that I also find the etymologies themselves interesting. More work than just making up silly memorable stories, sure, but what do you expect from a lingweenie? :)

perjudicial: damaging, harmful, detrimental

From perjudicar: "Ocasionar daño o menoscabo material o moral." Looks like it's related to English injury.

precavido: cautious, prudent

From precaver: "Prevenir un riesgo, daño o peligro, para guardarse de él y evitarlo." May be related to English precaution? Think of the "v" in precavido being that Latin "u/v", so it's really precauido (but not really), which is more like precaution.

precipitado: hasty, rash

From precipitarse: "Arrojarse inconsideradamente y sin prudencia a ejecutar o decir algo." From Latin praecipitāre "to throw or cause to fall headlong," from which English precipitation comes. Rain is water falling headlong to earth, right? That hasty precipitation, has no parachute! :)

And the other set of words giving me trouble:

terco: stubborn, obstinate

The RAE has no etymology for this one. :( Think of someone being a turkey, which as "a stupid, slow, inept, or otherwise worthless person" isn't quite the same, but gets in the right ballpark of semantics, anyhow.

tosco: coarse, rough, crude, unrefined

From Vicus Tuscus, "el barrio etrusco, por alusión a la gente libertina que vivía en esta zona de Roma." So the folks on Etruscan Street were rough, crude, unrefined folks, apparently.

áspero: coarse, rough, harsh

"Insuave al tacto, por tener la superficie desigual, como la piedra o madera no pulimentada, la tela grosera, etc." Compare English asperate (which you didn't know existed): "To make rough or uneven in surface, rugged or harsh in sound, manner, etc" from the same Latin root asper. Although unrelated, think of an aspirated voice being rougher.

asqueroso: disgusting, filty, revolting

"Que causa o tiene asco." From Greek ἐσχάρα, which literally meant hearth. English scar is ultimately from the same origin as Spanish asqueroso: ἐσχάρα hearth → the mark of a burn (from said hearth) → scar the trace of a healed burn (or other wound). Scars and burns can be disgusting, right? So scars are asquerosos.

Update, 9:45 PM: It's already working for me! I just did some of the flashcards again, and this time I finally got all of them right! Wootles.

Spanish definitions and etymologies are from the Real Academia Española; the English ones are from the Oxford English Dictionary.