Why do we call it the “Spanish” flu?

The designation of the 1918 pandemic as “Spanish” flu is a misnomer, as no evidence suggests the pandemic originated in that country or was more severe there than elsewhere. The first cases were detected in Europe and the USA. As Spain was neutral during the first world war, its media covered the epidemic there without restraint. The popular association of the 1918 pandemic with Spain (in name only) is thought to have arisen from that high-profile news coverage.

From WHO  web site