leading (n.1) Look up leading at Dictionary.com
"lead work; lead covering or frame of lead," mid-15c., verbal noun from lead (n.1). Printing sense is from 1855.
leading (n.2) Look up leading at Dictionary.com
mid-13c., "a bringing by force," verbal noun from lead (v.1). Meaning "direction, guidance" is from late 14c.
leading (adj.) Look up leading at Dictionary.com
1590s, "that goes first," present participle adjective from lead (v.1). Meaning "directing, guiding" is from 1620s. Of persons, "having first or most prominent place," 1670s. In reference to theatrical companies, leading lady is from 1846; leading man from 1847.