Yet another word that interests me due to its unknown etymology.  What is it about words with uncertain histories that so intrigues me?

dither (dith·er): / DITH er /
intransitive verb

(1) to tremble or shiver, especially with excitement or fear; to quiver
(2) to vacillate; to act indecisively or irresolutely; to be nervous or agitated

noun

(1) a state of nervous agitation, flustered excitement, fear, or indecisiveness; confusion
(2) a trembling or vibration

[Alteration of obsolete ‘didder’ meaning “to quake, tremble, shake,” from Middle English ‘didderen’ meaning “to tremble,” ultimately from an uncertain origin.]

Usage: There are times when trying to write that I ultimately dither from lack of inspiration or an inability to focus.