f words which have come down to us from the English
language of a thousand years ago have nearly all changed their
meanings.

We have two of these old words which have now each two exactly
opposite meanings. The word _fast_ means sometimes "immovable," and
sometimes it means the exact opposite--"moving rapidly." We say a key
is "fast" in a lock when we cannot get it out, and we say a person
runs "fast" when we mean that he runs quickly. The first meaning of
steadiness is the original meaning; then the word came to be used to
mean "moving steadily." A person who ran on, keeping up a steady
movement, was said to run fast, and then it was easy to use the word
for rapidity as well as steadiness in motion or position. This is how
the word _fast_ came to have two opposite meanings.

Another word, _fine_, has the same sort of history. We speak of a
"fine needle" when we mean that it is thin, and a "fine baby" when we
mean that it is fat. The first meaning is nearer to the original,
which was "well finished off." Often a thing which had a great deal of
"fine" workmanship spent on it would be delicate and "fine" in the
first sense, and so the word came to have this meaning. On the other
hand, the thing finished off in this way would generally be beautiful.
People came to think of "fine" things as things to be admired, and as
they like their babies to be fat, a fat baby will generally be
considered a fine baby. It was in this kind of way that "fine" came to
have its second meaning of "large."

The common adjectives _glad_ and _sad_ had quite different meanings
in Old English from those they have now. In Old English glad meant
"shining," or "bright," but in a very short time it came to mean
"cheerful." Now it means something rather different from this, for
though we may speak of a "glad heart" or "glad spirit," such
expressions are chiefly used in poetry. Generally in ordinary speech
when we say that we are "glad" we mean that we are pleased about some
special thing, as "glad that you have come."

_Sad_ in Old English meant to have as much as one wanted of anything.
Then it came to mean "calm" and "serious," perhaps from the idea that
people who have all they want are in a mood to settle down and attend
to things seriously. Already in Shakespeare's writings we find the
word with its present meaning of "sorrowful." It has quite lost its
earlier meaning, but has several special new meanings besides the
general one of "sorrowful