A Dictionary of Music and Musicians/Manier
MANIER, (Ger.), lit. 'manner'; derived, like our word 'manner,' through the French manière, a manner, and manier, to handle, from the Latin manus, a hand. It has two entirely distinct meanings, one dealing with the æsthetics of music, the other with its technicalities. In the first of these connections the word signifies 'mannerism,' or the faulty adherence to some peculiarity in style, bringing such peculiarity into undue prominence. It is the abuse of individuality, without which quality no composer can be truly great. The German word is always used in this sense of reproach; it never has the meaning of 'individuality.'
The second meaning of the word is the same as the French agrémens, ornaments introduced into, and built upon, the melody, whether indicated by small notes, or marks, or added at the will of the performer. [See Agrémens, vol. i. p. 42, where the subject is fully treated.][ J. A. F. M. ]