Etymology – the history of a word
Knowing a word's origin means knowing how that word got started in the first place. You can find out about a word’s history, called its etymology, from a dictionary. Using a print dictionary or Merriam-Webster online, http://www.m-w.com/, look up words and figure out how their history tells you about their essential meaning.
Example: Look up window. You'll find that it comes from the Middle English (ME) windowe, which came from the Old Norse (ON) vindauga, which itself was formed from the two Old Norse words vindr, which meant "wind," and auga, which meant "eye." So window once meant "wind-eye," a poetic description appropriately suggesting a window's function of letting in both air and light.