Reading Margaret Visser's The Gift of Thanks and coming across fascinating bits of info and insight:

"German danken ('to thank') is related to denken (English 'to think'). 'Thank' and 'think' are one: a person given what he or she wants does not just grab the thing that satisfies, but takes the trouble to think about who gave it and what this giving means. Gratitude is not only an emotion, but also a matter of thought -- a form of awareness."

Also, "The English word smile has the same Indo-European root as milagro [miracles]." Love that.

And I find it interesting that she links Hobbes' views with King Lear's Edmund.

Later on she writes about related gestural manifestations like the tradition of kowtow, about the origins of bowing and curtsying:

"In the Middle Ages men knelt on two knees to God and on one to their superiors; women knelt on both knees to both God and human beings. Ceremonial kneeling to other people was known in the sixteenth century as a courtesy, which was behaviour refined enough to be the habit of courtiers. Bowing (the word rhymed with rowing) meant gracefully lowering the body by bending one or both knees.

By the nineteenth century the bow (now rhyming with bough) came to require rigid knees and bending the torso forward from the waist only. 'Courtesying,' shortened to 'curtsying,' now meant lowering the body by bending both knees -- with adjustments contributed by the feet -- and simultaneously increasing one's width by spreading one's skirts. This gesture became the female equivalent of a bow. . . It has been suggested that curtsying is inherently more submissive than bowing because it lowers the whole body."

Such a great read so far!