The Hebrew word תֵּבָה (tebah) occurs 28 times in the OT and simply means (literally), chest, box, coffin, etc. That is, a box-like container used to house and protect some contents that are (by definition) precious. See BDB meaning in appendix below.
Interestingly, the noun is only ever used to describe just two objects:
- Noah's ark - the great ship, 26 places in Gen 6-9
- Moses' ark of reeds line with pitch in Ex 2:3, 5
Given the basic meaning, it is not surprising that that such a word is used for these objects. What is surprising is that the word used for "ark of the covenant". In the latter case, the word is אָרוֹן (aron) which means "sarcophagus" and is only used to describe a box containing inanimate things such as:
- 2 Kings 10:10 - chest for money
- Gen 50:26 - Joseph's sarcophagus
- Judges 20:27, the tables of stone with the 10 commandments, etc
Thus, I suppose it is appropriate that תֵּבָה (tebah) describes a box containing people, animals and Moses; while אָרוֹן (aron) describes a box containing dead things like money a dead bodies and the law.
APPENDIX
BDB meaning for תֵּבָה (tebah)
תֵּבָה noun feminine ark (properly chest, box (compare Late Hebrew תֵּבָה); probably Egyptian loan-word from T-b-t, chest, coffin (Brugsch, ErmanZMG xlvi (1892), 123); > Babylonian word JenZA iv (1889), 272 f. HalJAssyr., 1888 {Nov.-Dec.}, 517); — absolute ׳ת Genesis 7:1 +; construct תֵּבַת Genesis 6:14; Exodus 2:3; — vessel in which infant Moses was laid among reeds Exodus 2:3 (made of papyrus, גֹּמֶא), Exodus 2:5 (both E; ᵐ5 θῖβις, θήβη, compare LewyFremdw. 100); vessel which saved Noah and his family, with animals, during flood (ᵐ5 κιβωτός): Genesis 7:1,7,9,17,23; Genesis 8:6,9 (twice in verse); Genesis 8:10,13; Genesis 9:18 (all J), Genesis 6:14 (made of עֲצֵי נֹפֶר), Genesis 6:14; Genesis 6:15; Genesis 6:16; Genesis 6:16; Genesis 6:18; Genesis 6:19; Genesis 7:13,15,18; Genesis 8:1,4,16,19; Genesis 9:10 (all P).