The letter "k" is rarely seen in Spanish. What is the origin of Spanish words containing a k? Are most recent loanwords from modern languages, influences from older languages (Latin or Greek), or of an even earlier origin?
According to the Wikipedia page for the Spanish language, under "Writing system", they are all loanwords (directly integrated or words "adapted" to the Spanish writing system):
The single origin for each word is obviously different, and I think we should go singularly. But the main point is that I don't think there are "native" Spanish words with a "K". I say "native", because after a while, any loanword (if used by people) becomes a legitimate word in a given language.
Most of the words containing a k come from foreign languages. For example:
There are, obviously some words that are names of people or places:
There are also words that come from names:
On the other hand, Spanish come from Latin and Greek and the 'k' letter comes from the 'kappa' Greek letter. So I think the words that come directly from Greek can be considered original words. For example all the words starting by kilo:
Some of the foreign words that contain the 'k' letter are translated using the 'qu'. For example:
"K" also has a seemingly widespread slang use in texting / SMSing and online chatting.
In this case it stands for the words
Also I wouldn't be surprised if there are some words borrowed from Native American languages such as Quiche and Quechua that are spelled with "k" at least informally and regionally. I think I've seen it on signs in Chiapas and Guatemala but I can't say for sure.