Ingrid babbles, as babies do. And babies start out with a predictable array of first sounds – the easy ones that arise naturally as the mouth experiments with various positions. Da da da and ba ba ba and um um um and so on.

In some languages the parents have, understandably, happily appropriated those sounds and provided them with meaning: daddy and mummy, or pappa and mamma. But not in Estonian! Estonian mothers have pulled off an incredibly clever trick. They call themselves “ema” or “emme” – but they call dads “isa” or “issi”. Unable to pronounce the s sound, babies are forced to focus all attention on their mothers, and it will be many months, if not years, before they can call their dads.