idiosyncratic metaphorical expressions

"there are idiosyncratic metaphorical expressions that stand alone and are not used systematically in our language or thought. These are well-known expressions like the foot of the mountain, a head of cabbage, the leg of a table, etc. These expressions are isolated instances of metaphorical concepts, where there is only one instance of a used part (or maybe two or three). Thus the foot of the mountain is the only used part of the metaphor A MOUNTAIN IS A PERSON"(#60 1029)
"their used part may consist of only one conventionally fixed expression of the language, and they do not systematically interact with other metaphorical concepts because so little of them is used." (#60 1037)
"Examples like the foot of the mountain are idiosyncratic, unsystematic, and isolated." (#60 1041)
"It is important to distinguish these isolated and unsystematic cases from the systematic metaphorical expressions we have been discussing." (#60 1046)