Both Uses of

mannerism
in
Lucky, by Sebold

The reason why I said that I had a feeling at that point was because I had only seen his back and his mannerisms at that point.†
Chpt 11 *

mannerisms = things done in a certain manner (or way)

I had a feeling, because of his build and mannerisms on the first time, when I saw him from the back, but since I had then not seen his face at that time, I was not sure.†
Chpt 11

Definitions:

(1) (mannerism)
an unusual behavioral trait
The exact meaning of mannerism can depend upon its context. For example:
- "a distinctive mannerism" -- an unusual behavioral trait such as rubbing the chin while listening to someone
- "a nervous mannerism" -- a distinctive gesture such as thumb twiddling or something else done with hands, body, or voice
- "an affected mannerism" -- an attempt to make an impression by speaking, dressing, behaving, or doing things in an exaggerated or unnatural way
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

Much more rarely, Mannerism can refer to the Mannerism style of painting -- a manner of painting common in 16th-century Europe and characterized by elongated human forms and vivid colors.