Vacuum's Two U's

Why does "vacuum" have two u's, IN A ROW?  It's a weird word.  But, looking at another double-u word might help our understanding: "continuum".  This totally makes me think of the bad guy we love to hate, and his immortal omnipotent (sort of) race in Star Trek, the Q.  Not to be confused with the "collective", which is Borg.  Anyway.  We actually use a recognizable root of "continuum", so it is easier to see that the last "um" is a suffix to indicate something about word forms.  To quote Matthew Lancey on Quora.com, "Double U was/is fairly common in Latin because of its complex system of word endings to indicate case, gender and so on."

So.  "Continue" (back in Latin spelled "continuare") becomes "continuum" when the verb becomes a noun*, and "vacare" or something like it becomes "vacuus" (adjective?) and "vacuum" (noun?) in Latin.  Etymology Online says that the word is probably a loan-translation from the Greek "kenon" which only slightly resembles "vacare", "vain", or "vacuus" - all of which are attested words in the family tree of "vacuum".  We had the great idea back in the 17th century English speaking world of spelling "vacuus" as "vacuous", which is clearer on the pronunciation and only slightly less obviously Latin.

A lot of sources online (really reliable ones like Yahoo Answers) say that there are two u's because how else would you know to pronounce two different vowel sounds there?  But, um, I don't really think that's how words work.  These people are either gullible, or bluffing the Internet looking for the gullible.

What I really want to know is why there is only one "c".  If there are ever seemingly pointless double consonants in words, it tempts me to double other lletterrs also. ("Embarrass", anyone? There are two doubles, and I spell it wrong the first time, every time.) Just saying.  Though I must say that if the "c" were a "k" like it should be, for some reason I wouldn't feel the need to double it in the same way.  But then, the vowel's pronunciation would bother me.  And if we insist on leaving only one "c" in our English transliteration, could we pronounce the "a" as a long "a" like in "bacon"?  Or maybe we could try "bacoon", "baakon", "bakun", "bacconn"?

*In my life, I am much more tempted to turn nouns into verbs.  I imagine this is historically predominant, also.  Therefore, when I am keeping my tone intentionally casual, I say things like "churching", "small-group-ing", "dishes-ing".  Verbs are a lot more fun, if they have a description built into them.  My preschool-teacher-friend also says that kids initially think much more in pictures than in words, so it is good if we can keep our speech so vividly picturey.

To God be all glory.