A primitive root perhaps originally to intensify, i.e. Treble; but apparently used only as denominative from shalowsh, to be (causatively, make) triplicate (by restoration, in portions, strands, days or years) -- do the third time, (divide into, stay) three (days, - fold, parts, years old).
1) to do a third time, do three times, divide in three parts 1a) (Piel) to do a third time, divide into three parts 1b) (Pual) to be three years of age, be threefold Part of Speech: verb A Related Word by BDB/Strong’s Number: a primitive root perhaps originally to intensify, i.e. treble Same Word by TWOT Number: 2403
Brown-Driver-Briggs
I. [שִׁלֵּשׁ] Pi`el denominativedo a third time, devide into three parts, etc.; — Perfect2masculine singular וְשִׁלַּשְׁתָּ֫Deuteronomy 19:3divide land into three parts (so Imperfectוַיְשַׁלֵּשׁ אֶתהָֿעָם [for ᵑ0וַיְשַׁלַּח] 2 Samuel 18:2ᵐ5L Bu); 1 Samuel 20:19stay three days (compare Dr); 1 Samuel 20:20 We Dr and others (compare ᵐ5) read ׳אֲשַׁלֵּשׁ בַּ (for ׳שְׁלשֶׁת הַ)=I will shoot on the third day with the arrows (HPS question); Imperfect3masculine plural וַיְשַׁלֵּ֑שׁוּ1 Kings 18:34, and Imperative masculine plural שַׁלֵּ֑שׁוּ1 Kings 18:34do a third time.
Pu`alParticipleמְשֻׁלָּשׁthree years oldGenesis 15:9 + 1 Samuel 1:24 (read with ᵐ5 Th We etc. בְּפַר מְשֻׁלָּשׁ for בְּפָרִם שְׁלשָׁה), feminine מְשֻׁלֶּשֶׁתGenesis 15:9 (twice in verse); הַחוּט הַמְשֻׁלָּשׁEcclesiastes 4:12the threefold cord; female plural מְשֻׁלָּשׁוֺתEzekiel 42:6three-storied chambers.
Genesis 15:9 HEB:לִי֙ עֶגְלָ֣ה מְשֻׁלֶּ֔שֶׁת וְעֵ֥ז מְשֻׁלֶּ֖שֶׁת NAS: to him, Bring Me a three year KJV: me an heifer of three years old, and a she goat INT: Bring heifer A three female year
Genesis 15:9 HEB:מְשֻׁלֶּ֔שֶׁת וְעֵ֥ז מְשֻׁלֶּ֖שֶׁת וְאַ֣יִל מְשֻׁלָּ֑שׁ NAS: Me a three year old KJV: and a she goat of three years old, and a ram INT: A three female year ram old
Genesis 15:9 HEB:מְשֻׁלֶּ֖שֶׁת וְאַ֣יִל מְשֻׁלָּ֑שׁ וְתֹ֖ר וְגוֹזָֽל׃ NAS: year old heifer, KJV: and a ram of three years old, and a turtledove, INT: year ram old turtledove young
Deuteronomy 19:3 HEB:לְךָ֮ הַדֶּרֶךְ֒ וְשִׁלַּשְׁתָּ֙ אֶת־ גְּב֣וּל NAS: the roads for yourself, and divide into three parts the territory KJV: giveth thee to inherit, into three parts, that every slayer INT: shall prepare the roads and divide the territory of your land
1 Samuel 20:19 HEB: וְשִׁלַּשְׁתָּ֙ תֵּרֵ֣ד מְאֹ֔ד NAS:When you have stayed for three days, you shall go down KJV:And [when] thou hast stayed three days, [then] thou shalt go down INT:have stayed shall go quickly
1 Kings 18:34 HEB:וַיִּשְׁנ֔וּ וַיֹּ֥אמֶר שַׁלֵּ֖שׁוּ וַיְשַׁלֵּֽשׁוּ׃ NAS: And he said, Do it a third time, and they did it a third time. KJV: And he said, Do [it] the third time. And they did [it] the third time. INT: A second said Do A third
1 Kings 18:34 HEB:וַיֹּ֥אמֶר שַׁלֵּ֖שׁוּ וַיְשַׁלֵּֽשׁוּ׃ NAS: Do it a third time, and they did it a third time. KJV: Do [it] the third time. And they did [it] the third time. INT: said Do A third
Ecclesiastes 4:12 HEB:נֶגְדּ֑וֹ וְהַחוּט֙ הַֽמְשֻׁלָּ֔שׁ לֹ֥א בִמְהֵרָ֖ה NAS: him. A cord of three [strands] is not quickly KJV: shall withstand him; and a threefold cord INT: him A cord of three is not quickly
Ezekiel 42:6 HEB: כִּ֤י מְשֻׁלָּשׁוֹת֙ הֵ֔נָּה וְאֵ֤ין NAS:For they [were] in three stories and had no KJV:For they [were] in three [stories], but had not pillars INT: for three in and had