hecka (hek` - uh) adv.(deriv. "heck of a")
Very; really; extremely; definitely; totally.
The folk etymology of words like "hella" and its less vulgar variant "hecka" is mysterious, but it's very obvious that both words are merely shortened versions of "hell of a" (or "helluva") and "heck of a", which are commonly used to express admiration and awe at some particular item.
Originally, "heck of a" would precede some noun, as seen in the following example:
That's a heck of a compound fracture there, Johnny. Let's hope the ambulance gets here fast.
This previous example had the obvious connotation that "heck of a" implied "really" + adjective. Whether something was really BAD or really GOOD didn't matter: it was certainly a "heck of a" something.
However, "hecka" as an adverb instead tends to precede adjectives, limiting itself to a substitute for the word "really" only, as seen in the example:
That lead singer for No Doubt is hecka fine, and I wish to procreate with her many times. (rhyming unintentional)
The words hella and hecka first gained notoriety in the Bay Area, eventually spreading through the usual circles (the Internet, population dispersal, popular culture) into the mainstream vocabulary of American youth. It is not known whether these phrases have gone intercontinental, but they may have potentially eaten French toast.
The venerable MALTP informs me that hir cousin from the Bay Area used the words hella and hecka with certain adjectives only, never crossing paths. When confronted with this fact, said cousin noted, "If you used 'hecka crazy', people would know you weren't from the Bay." So perhaps the tamer variant implies more innocent observations, such as, "My dog is hecka smart. He just solved Fermat's Last Theorem." Another possible explanation is that it is considered bad form to mix the "k" phoneme in "hecka" with other "k" sounds, i.e. "hecka crazy", "hecka cool", "hecka cumulonimbus."
UPDATE: "Hecka" Found In Ancient Usenet Post
That's right, kids. It seems that on March 19, 1992, one auerbach@sleepy.bmd.trw.com referred to himself as "hecka picky" regarding his mate-selecting habits. This comes three years after the first sighting of the adverb "hella" in a Usenet post. A point of interest is that his domain name contains the word sleepy - the urban mythology of hecka suggests that dazed and confused stoners in their early morning stupor would mumble "heck of a", transforming it into "hecka." Of course, this is merely a coincidence ... or is it?
Sources:
http://instruct1.cit.cornell.edu/courses/ling100_4/DLU-Stav99/DLU-H.html
http://groups.google.com/groups?q=hecka&start=700&hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&scoring=d&selm=1992Mar19.125029.29%40sleepy.bmd.trw.com&rnum=70440sleepy.bmd.trw.com&rnum=704