Bonkka or bonker is an East Anglian (Norfolk) word meaning "very large" or "a big strapping person"; and is frequently applied to young girls (CN2).
The Bonnka owner goes aboard the Bonnka at the Lake, and finds Ratty in her. The Death and Glories have alighted near the Lake, leaving Ratty behind. They run to the Lake: and Joe leading, finds her. They see the owner smoking a pipe and feeding Ratty bread and milk. He becomes fast friends of the Death and Glories, puts them up for the night (CN: It's Gone) and the next day takes them for a cruise on the Lake. They meet the Swallows, Amazons and D's (CN: One Way of Meeting Nancy). He is never named (like the owner of the Cachalot).