The name is very old village name (). The suffix simply means 'built', but the meaning of the first part of the name has no definite interpretation. Several old village names end in
-bú, and in those cases the prefix refers to nearby place names. For example, the prefix in the name of
Selbu Municipality () is named after Seli which is the original name of the lake
Selbusjøen. A name of a nearby place such as could be the source of this name. Once possibility is the noun , which means 'red', 'anchorage', or 'open harbor', or the verb , which means 'swing', 'crank', or 'anchor'. One possibility is that the nearby bay could have been historically named something like with the meaning 'anchorage' or 'harbor'. The nearby Åker farm was an older
Iron Age residence for powerful chiefs and small kings. Therefore it is likely that the meaning of the current name
Ridabu was originally , which means a village 'built near Ríði' (a bay now called
Åkersvika). ==References==