'slant' originates from Middle English (e.g. 'slenten' / 'slaunt'), likely from an older Germanic root meaning 'to lean or slope'.

'slant' changed from Middle English forms such as 'slenten' (meaning 'to lean or slope') and gradually shortened/spelled into the modern English word 'slant'.

Initially it meant 'to lean or slope'; over time it acquired extended senses such as 'a particular way of presenting information' (i.e., bias).