Until about 1920, in western countries little boys of varying ages (but seldom more than six or seven) wore dresses before being 'breeched' (given their first pair of trousers) after which they did not wear skirts again. The origin of the younger boys wearing dresses may be simply that before about 1550, both sexes and all ages wore skirted garments: tunics and gowns, and children's styles were often slow to change. A young child in the medieval and early Tudor period, once past the age of swaddling, had worn a simple and extremely practical loose-cut gown or coat, either knitted or made of cloth and usually with a round neck and long sleeves. The dresses in question were boys' dresses, made and worn as such, and not to be confused with girls' clothing: the cut, fabrics, accessories and colours are usually clues to the differentiation of gender. Boys' dresses were often made in stronger colours than those for girls, and sometimes showed a certain amount of exaggeration, particularly in details such as belts, metallic buttons, and tailored appearance.

Other theories to account for the custome of young boys wearing dresses include the idea that all children of this age were considered more or less as babies and so wore the same type of garments; that it was appropriate for the boys to wear skirts because young children were cared for by women rather than men; that it protected the legs of young children if they fell while learning to walk; that it would be easier to change nappies. In fact the age for breeching suggests that making it easier for young boys to urinate or defecate is perhaps the main explanation. This would be especially true when breeches or trousers had complicated fastenings which took a long time to undo.

Putting dresses on boys was emphatically not treating them as girls, just as dressing girls in trousers from the 1930s onward was not treating them as boys. And as all the younger boys wore dresses, they would not have felt conspicuous in skirts, although they undoubtedly looked forward to getting their first trousers and being thought of as more grown up.