The term 'most knowledgeable' can be described by two six-letter words: 'sagest' and 'ablest'. 'Sagest' is an adjective that means having or showing great wisdom or sound judgment. It is derived from the Middle English word 'SAGE', which means wise. 'Ablest' is an adjective that means having or showing great skill or ability. It is derived from the Old English word 'ABLE', which means capable. Together, these two words describe someone who is the most knowledgeable, possessing both wisdom and skill.