Some facts about how word meanings change over time. This is not an entire lesson plan, but just some notes on meaning change.
Did you know...?
Sometimes the meanings of words get narrower:
In Old English, the word Hund meant dog, but in modern English hound refers to a particular type of dog.
In Old English gume meant jaw, palate, inside of the mouth, but the meaning narrows in Middle English, where gome means gum. And it does in Modern English too!
In Early Modern English the word acorn, which formerly meant fruits, narrows to fruit of an oak tree.
Courage, which meant heart, mind, disposition, nature, bravery, valor narrowed to bravery, valor.
Sometimes the meanings of words get broader:
The Old English word dogge, referred to a particular breed of dog, and today refers to domestic canines in general.
In Old English bridd meant young bird, but the meaning of this term broadened in Middle English, where bird came to mean fowl of any age.
The word twist used to mean twig, tendril, or branch, but after the 17th century its meaning broadens to mean the action of twisting something, and anything that has been twisted (such as a slice of lemon, a wire, yarn).
Decimate for the Romans meant to kill every ten soldiers, but now its meaning has broadened to mean destroy, utterly wipe out, annihilate.
(Can you think of other words that have the morpheme deci- and have to do with ten? decimal, decade, decathlon)
Sometimes the meanings of words get better, or shift to a more positive meaning; this is called amelioration.
The word croon, for example, which in English means to sing softly, comes from Dutch kronen, which means to groan or lament.
Words can also shift in denotation, shifting to mean something else entirely. For example, blush used to mean look/gaze, and in Early Modern English came to mean to redden in the face (from shame or modesty).
The term moody in Old English meant brave, and now means given to changeable emotional states.
Some current innovations are bad for good, and sweet for exceptional. Awesome, which used to mean inspiring awe or full of awe, in current speech usually means remarkable, staggering, prodigious. Though shifts in meaning are inevitable, people who view language change as language degeneration bemoan the loss of earlier meanings. They lament the fact that aggravate, which originally meant to worsen, is now used to mean irritate, and that the meaning distinction between the verbs imply and infer, and affect/effect is less and less clear in modern usage.