tlanitztli.

Headword: 
tlanitztli.
Principal English Translation: 

the shin of the leg (see Molina); the shin bone (see Karttunen)

For a hieroglyph that involves this noun, see:
https://aztecglyphs.wired-humanities.org/content/tlanitztlan-15v

IPAspelling: 
tɬɑniːtstɬi
Alonso de Molina: 

tlanitztli. espinilla dela pierna.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 129r. col. 1. Thanks to Joe Campbell for providing the transcription.

tlanitz to. la espinilla dela pierna.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 129r. col. 1. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

TLANĪTZ-TLI shin bone / espinilla de la pierna (M) This is abundantly attested but only in T. It appears to be related to TLANCUĀ(I)-TL ‘knee.'
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 286.

Attestations from sources in English: 

See an image that represents tlanitztli in the Visual Lexicon of Aztec Hieroglyphs, ed. Stephanie Wood (Eugene, Ore.: Wired Humanities, 2020-present).

Totlanitz. Itechpa mitoa: in mohoquichitoa aca, in quitoa: ca nitiacauh, ca nitlamani, ca yaoc nimatini...no ioan tiquitoa: ninotlanitztia, timotlanitztia. = Our shin. This is said about the person who speaks of his prowess. "I am a captain," he says to someone. "I have captured prisoners and am experienced in war."...And we also say: I boast falsely, you boast falsely.
Thelma D. Sullivan, "Nahuatl Proverbs, Conundrums, and Metaphors, Collected by Sahagún," Estudios de Cultura Náhuatl 4 (1963), 106–107.

themes: 
Anatomy