Origin and history of tidal

Middle English tide "time, season; recurring interval, space of time," especially as regards a particular purpose or natural process, from Old English tīd "point or portion of time, due time, period, season; feast-day, canonical hour," from Proto-Germanic *tīdi- "division of time" (source also of Old Saxon tid, Dutch tijd, Old High German zit, German Zeit "time"), according to Watkins from PIE *di-ti- "division, division of time," suffixed form of root *da- "to divide."

The "time" senses in English mostly are archaic. Compare tidings, betide, tidy (adj.), also Middle English anytide "any time," tideful "seasonable, opportune, timely, fitting" (c. 1300). Old English uhtan-tid was early morning, the period before dawn (with uhte "daybreak"); tide-song was the divine service peculiar to a canonical hour.

In the alliterative pairing of time and tide (early 13c.) the words are synonyms, originally indicating "on all occasions" or "as warranted." Nares writes that the Puritans preferred -tide in festival names to -mas.

The main modern meanings "time of the tide" (c. 1300), "rise and fall of the sea, flow of the tidal current" (mid-14c.) probably are via the notion of "fixed time" (compare Old English morgentid "dawn," Middle English dai-tide "daytime"), specifically "time of high water." This is either a native evolution or from Middle Low German getide (compare Middle Dutch tijd, Dutch tij, German Gezeiten "flood tide, tide of the sea"). Figurative use by late 14c.

Old English seems to have had no specific word for this, using flod and ebba to refer to the rise and fall. Old English heahtid "high tide" meant "festival, high day."

Tide-mark "limit of the ebb or flow of a tide" is by 1753; tide-pool, left by regress of the sea, is by 1849. Tide-table, showing the times of the daily tides, is by 1590s.

"large wave which rolls over and inundates the land," 1896, in reference to the one that struck Japan that year on June 15, from Japanese tsunami, from tsu "harbor" + nami "waves."