slog (v.) Look up slog at Dictionary.com
1824, "hit hard," probably a variant of slug (v.3) "to strike." Sense of "walk doggedly" first recorded 1872. Related: Slogged; slogger; slogging.
slog (n.) Look up slog at Dictionary.com
1846, "a hard hit," from slog (v.). Sense of "spell of hard work" is from 1888.