We speak of a person being the "tool" of another, and this is a metaphor taken from the general idea of work. The "tool" is merely used by the other person for some purpose of his own, just as a workman uses his tools. The greatest poem, or book, or picture of a poet, writer, or painter is often described as a "masterpiece." This word now means a "splendid piece of work," but in the Middle Ages a "masterpiece" was a piece of work by which a person working at a trade showed himself sufficiently good to be allowed to be a "master." Before that he was a "journeyman," and worked for a master himself, and, earlier still, an apprentice merely learning his trade. We often now use the expression to try one's "'prentice hand" on a thing when we mean that we are going to do a thing for the first time.
The commonest actions have naturally given us most metaphorical words, for these were the actions of which the word-makers were most easily reminded. We speak of our passions or emotions being "kindled," taking the metaphor from the common action of lighting a fire.
The two words lord and lady contain very homely metaphors. The lord was the "loaf-keeper," in Old English hlaford, the person on whom the household depended for their food. The lady might even make the bread, and often did so; and the word lady comes from hlæfdige—dig being the Old English word for knead.
The common word maul may mean to beat and bruise a person, but it means more often merely to handle something carelessly and roughly. Literally it means "to hit with a hammer," and comes from maul or mall, the name of a certain very heavy kind of hammer; so that when a child is told not to "maul" a book, it is literally being told not to hit it with a heavy hammer.
We have made many metaphorical words from joining together two Latin words and making a new meaning. We speak of a person having an "obsession" about something when he is always thinking of one thing. But the word obsession comes from the Latin word obsidere, "to besiege;" and so in the word obsession the constant thought is pictured as continually trying to gain entrance into the mind. We use the word besiege in the same metaphorical sense. We speak of being "besieged" with questions, and so on.
Another word used now most often metaphorically comes also from this idea of siege warfare. In all fortified places there are holes at intervals along the walls of defence, through which the defenders may shoot at the attackers. These are called "loop-holes." This word is now used much oftener in a figurative sense than to describe the actual thing. When two persons are arguing and one has plainly shown the other to be wrong, we say he has "not a loophole" of escape from the other's reasoning. Or if a person objects very much to doing something, and makes many excuses, every one of which is shown to be worthless, we again say he has "no loophole for escape."
Every child has heard of the Crusades, in which the nobles and knights and soldiers of the Middle Ages went to fight against the Turks to win back the Holy Sepulchre. These wars were called "crusades," from the cross which the Crusaders wore as badges. The word was made from the Latin word crux, which means "cross." But crusade has now become a general word. We speak of a "temperance crusade," of a "peace crusade," and so on. The word has come to have the general meaning of efforts made by people for something which they believe to be good; but literally every person who works for such a "crusade" is a knight buckling on his armour, signed with the cross, and sallying forth to the East.
This word sally also comes from siege warfare. A "sally" means a rush of defenders from a besieged place, attempting to get past the besiegers by taking them by surprise. It also has the more general meaning of an excursion, such as the going forth to a crusade. It means literally a "leaping out," and comes from the Latin word salire, "to leap." The word sally is also used to mean a sudden lively remark generally rather against some person or thing. It is interesting to notice that the fish salmon also probably takes its name from this Latin word meaning "to leap."
Any child with a dictionary can find for himself many hidden metaphors in the commonest words; and he will learn a great deal and amuse himself at the same time.