watertight

Etymology

It is formed from English water + tight.^[2][3][4] The OED records an earlier form with thight, the older form of tight, as waterthight (1387–1673),^[2] and Merriam-Webster Unabridged gives the Middle English form as water thicht.^[5] Etymonline also gives a hyphenated spelling.^[3] The OED compares Middle Dutch waterdicht, now waterdicht in Dutch, and German wasserdicht, from the 17th century.^[2]

Earliest recorded meaning

Built or fitted so that water cannot leak in or out: first as waterthight in 1387, in an Edinburgh charter,^[2] and in the present form in 1489, in a Scottish notary's protocol book.^[2] Etymonline dates the word to the late 14th century.^[3]

Semantic evolution

The figurative sense, unassailable or without loopholes, of an argument, plan or agreement, appeared in 1647, in Nathaniel Ward's Simple Cobler of Aggawam.^[2][3] The phrase watertight compartment first described the sealed sections into which a large ship is divided for safety,^[6] and Collins records its use for anything kept strictly apart from other influences.^[7] As a noun the word meant watertightness in a Scottish record of 1539.^[2] Since 1829 it has also named a boot of this kind, usually in the plural.^[2]

Timeline

• 1387 – waterthight, not letting water through.^[2] Etymonline dates the word to the late 14th century.^[3]
• 1489 – watertight, in the same sense.^[2]
• 1539 – noun, watertightness (Scottish, obsolete).^[2]
• 1647 – figurative, without flaws or loopholes.^[2][3]
• 1829 – noun, a watertight boot.^[2]

Meanings

Adjective

1. Made or fitted so that water cannot pass in or out: a watertight seal on the hatch.^[7][5][2]
2. Having no loopholes or flaws; impossible to dispute or evade: a watertight alibi.^[7][5][2]
3. Kept strictly separate from other things or influences, especially in watertight compartments.^[7][6]

Noun

1. A watertight boot, usually in the plural.^[2]

Word family

• watertightness
• nonwatertight

Related words

• water
• tight

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m n o p Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
5. ^ a b c Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
6. ^ a b Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
7. ^ a b c d Collins English Dictionary (2023), Glasgow: HarperCollins