Lucifer comes from the Latin Vulgate:
quomodo cecidisti de caelo lucifer qui mane oriebaris corruisti in terram qui vulnerabas gentes --
Biblia Sacra Vulgata: Iuxta Vulgatem Versionem. (1969). (electronic edition of the 3rd edition., Isa. 14:12). Stuttgart: Deutsche Bibelgesellschaft.
The meaning in Latin:
Lūcĭfer, fēri, m. A. The morning-star, the planet Venus ... --
Lewis, C. T., & Short, C. (1891). Harpers’ Latin Dictionary (p. 1080). New York; Oxford: Harper & Brothers; Clarendon Press.
In Spanish:
lucero nm : bright star --
Merriam-Webster, I. (1998). Merriam-Webster’s Spanish-English dictionary. Springfield, MA: Merriam-Webster.
Thus, both mean morning star.
They are translating הֵילֵ֣ל
†הֵילֵל S1966 TWOT499a GK2122 n.m. appell. shining one, epith. of king of Babylon, אֵיךְ נָפַלְתָּ מִשָּׁמַיִם ה׳ בֶּן־שָׁ֑חַר Is 14:12 how art thou fallen, shining one, son of dawn! i.e. star of the morning. (Cf. Assyrian muštilil epith. of (Venus as) morning-star III R 57:60 OppJAS 1871, 448 Schr 1874, 337 COT ad loc.) --
Brown, F., Driver, S. R., & Briggs, C. A. (1977). Enhanced Brown-Driver-Briggs Hebrew and English Lexicon (p. 237). Oxford: Clarendon Press.
The LXX has:
ἑωσφόρος,-ου N2M 0-1-1-5-0=7
1 Sm 30,17; Is 14,12; Ps 109 (110),3; Jb 3,9; 11,17
morning star, morning 1 Sm 30,17
*Ps 109 (110),3 πρὸ ἑωσφόρου before the morning star, before dawn, or before Lucifer-מִשַּׁחַר for MT מִשְׁחָר?
Cf. TOURNAY 1960, 11–12; →NIDNTT --
Lust, J., Eynikel, E., & Hauspie, K. (2003). A Greek-English Lexicon of the Septuagint : Revised Edition. Deutsche Bibelgesellschaft: Stuttgart.
2 Peter 1:19 has:
φωσφόρος, ον bearing or giving light (Eur.+; pap., Philo); subst. ὁ φ. the morning star, Venus (Eur., Ion 1157; Ps.-Pla., Tim. Locr. 96E; 97A; Plut., Mor. 430A; 601A; 889A al.; Cicero, Nat. Deor. 2, 20; Vett. Val. 236, 6; Sib. Or. 5, 516) fig. 2 Pt 1:19. JBoehmer, ZNW 22, ’23, 228-33; FBoll, Sternglaube u. Sterndeutung4 ’31, 47f.—FJDölger, Antike u. Christentum V 1, ’35, 1ff interprets the ‘light-bearer’ to mean the sun (this mng. of φ. in Nicetas Eugen. 1, 87; 3, 21; 5, 258 Hercher); cf. HWindisch ad loc. M-M.* --
Arndt, W., Gingrich, F. W., Danker, F. W., & Bauer, W. (1979). A Greek-English lexicon of the New Testament and other early Christian literature : a translation and adaption of the fourth revised and augmented edition of Walter Bauer’s Griechisch-deutsches Worterbuch zu den Schrift en des Neuen Testaments und der ubrigen urchristlichen Literatur (p. 872). Chicago: University of Chicago Press.
Thus, some take φωσφόρος in 2 Peter 1:19 as meaning Sun instead of morning star. 2 Peter 1:19 does not have the Greek word for morning star that is in Isaiah 14:12.