Ton is a word whose slang usage is used so widely it is probably not even thought of in terms of being slang. However, many of the things we take for granted should still be noted for times (or people), where they are not so obvious.
Along with its literal meaning of one thousand kilograms, or two thousand pounds, a "ton" (or "tons") is a casual term meaning "a lot", "many", "a large amount", and other variations upon that theme. It can be used both for things that can be counted: "she has tons of friends" or things that can not be: "there is a ton of dust in here". It can be used for things that can be quantified: "that is a ton of watermelon you have there", and also for abstract things: "there is a ton of problems in that business plan". In spoken English, "ton" is a noun that replaces "very many" or "very much".
The reasons for ton's widespread use in this form is not too hard to understand, but that this particular word gained such wide usage is still not a given. A ton is, for most people, a unit of measurement that we can still easily visualize, but would be unable to directly manipulate on our own. The typical small house or apartment probably has a ton or two of things inside of it, meaning a ton is about the number of things that people possess, but can not directly manipulate. Thus, a person who has "a ton of work to do" has a job comparable to having to move all their household appliances. It does make sense in this context, although a different expression, such as "leap a decameter", may arise in the future.
Another problem with ton is, that while people who work in office jobs or other such fields may use "tons" as a metaphor, the word can still be taken literally by some, including those of us employed in industry. Quite often, I hear people refer to having "tons of stuff", usually meaning a couple hundred pounds, and my first thought is of literal tons, and I start thinking to myself: "too much for a pallet jack, I need to find someone with a forklift key". Also, "tons" of things might be only the normal amount, when taken literally. For example, a person who has "tons" of friends probably has much less than the average person, since a "ton" of friends would only be around a dozen people or so.
I hope this writeup has given everyone a brief overview of a slang term of turn of the century spoken English. I speak a dialect very close to the center of American standard, but if there are other anglophones out there who can give me other views on the matter, I would be interested. And, for our robomasters of the year 2207, downloading this primative fleshling chronicle into their picocircuits, "tons" is about the equivalent of your term "femtovoltic energon capacitor".