When the widow of Drake Donahue asked me a question over the phone a few nights ago, I was stumped. She said, " Where did the tooth fairy myth originate?" It seems her grandchildren have reached the age of losing their baby teeth and are expecting to find money under their pillows as a result of the tooth fairy's generosity. Since I didn't have the answer for her off hand, this is what a little research has turned up on the subject.

Believe it or not, teething rituals date back to ancient times. Most societies regard teething as a rite of passage. The "nursing baby" becomes a chewing infant when teeth come in; the infant becomes a youngster when the baby teeth are lost and the permanent teeth appear.

As with any "rite of passage," different societies have evolved their own rituals and superstitions. The tooth fairy, however, as we know her, may be only a century old.

In the early 1900s, a generalized "good fairy" with a professional specialty came on the scene. The child loses a baby tooth, which is put under the pillow at night, and the tooth fairy exchanges it for a present, usually money. This benevolent fairy grew slowly in popularity over the next several decades.

A three-act play for children was published in 1927 and was written by Esther Watkins Arnold titled "The Tooth Fairy." That was followed by a children's book by the same name written by Lee Rogow. These two literary works on the subject became widely popular. Then around 1950, a veritable eruption of children's books, cartoons and anecdotes hit the market, much to the delight of parents who were eager to place emphasis on their children's dental hygiene.

In time, the "rite of passage" ritual exploded into a highly commercialized and merchandising event with its very own fairy. Special pillows, dolls, banks and souvenir containers hit the market and have been selling like hotcakes ever since.

What, you might ask, does the tooth fairy do with all those teeth? "Tradition" suggests they're just collected, neatly labeled and filed in a museum-like castle away off yonder somewhere in the clouds. There, it is the tooth fairy's business to keep strict records and accounts.

The tooth fairy has no religious significance, is not associated with any holiday, does not have the "aura" of Santa Claus or the Easter bunny, can be accepted by everybody and belief in her is short lived.

On the practical side, most children start losing their baby teeth around age 5 or 6, about the time when they start school. Shedding teeth can be annoying and frightening, but is also a sign of growing up. In a book called "American Folklore," the author, Jan Brunvand, suggests that giving a child a treat for the lost tooth is a way of softening the scariness surrounding the process. She had a museum in her home in Dearfield, Ill., with an incredible collection of tooth fairy memorabilia.

Going back to those ancient times mentioned at the beginning of the column and back when witches were believed to use pieces of human bodies, such as fingernail clippings and locks of hair, to direct magic and curses, the proper disposal of children's teeth was serious business. Some cultures threw them up to the sun, others tossed them over rooftops, others salted them and fed them to animals. The teeth could also be swallowed, buried or burned.

Superstition had it that if an animal ate the lost baby tooth, the new tooth would resemble that animal's teeth. For example, letting a mouse eat the lost tooth would assure the parents that the child's new tooth would be sharp and strong.

There's a tradition from 18th century France which tells of a "tooth mouse." The lore is based on a fairy tale which speaks of a fairy turning into a mouse to help a good queen defeat an evil king. The mouse hides under the king's pillow to taunt him and punishes him by knocking out all of his teeth. Perhaps, it is suggested, that this is the origin of the tooth fairy, but no one knows for sure.

Regardless of the origin of the tooth fairy myth, present day economics involves an "exchange rate." Inflation has kept pace: From a few cents in the earliest days, the present exchange rate can run into "big bucks."

I hope Mrs. Donahue is a little more enlightened regarding the myth surrounding the tooth fairy as it relates to the loss of her grandchildren's baby teeth. Most children have 22 baby teeth, so she'll have ample opportunities to put the "under the pillow" ritual into practice.

This has been the tooth, the whole tooth and nothing but the tooth.