The story
Cafuné is Brazilian Portuguese for running your fingers slowly through someone's hair, for the pleasure of it. The usual phrase is fazer cafuné, 'to do cafuné', and a child will ask for one by name.
The Houaiss dictionary traces the word to kifune in Kimbundu, a Bantu language of Angola. Kimbundu speakers were among the millions of Africans taken to Brazil during the slave trade, and a number of everyday Brazilian words come from their language. Cafuné is one of the gentler ones.
English has the gesture but no noun for it. Caress is too general and can mean almost any touch, and 'stroking someone's hair' is a description, not a name. Cafuné picks out one particular touch: on the head, unhurried, and usually from someone close, a parent with a child or two people on a sofa.
A scene: a Sunday afternoon in São Paulo. A teenager has stretched out with her head in her grandmother's lap, and the grandmother, half watching a telenovela, works her fingers through the girl's hair until both of them nod off.
Brazilians use the word for animals too. A Brazilian guide to keeping parrots describes the bird coming back tame after a sulk and lowering its head to receive a cafuné.