The last image looks to be of an Italian 'roncola' with a round wooden handle - the 'knob' on a British billhook is known as a caulk, or more properly the handle is said to be caulked... A round handle is common on double edged billhooks, and one or two regional patterns of single edge billhooks have a round handle (Kent and Devon)....
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1st image UK caulked handles
2nd image Italian 'roncole' (pl) with integral hand guard
3rd image Dutch 'hiepen' (pl) - one of the few countries where a variation of the caulked handle is common