From Wiktionary, the free dictionary

In the senses of “overcrowd (a place)” and “impede (a person)”: from Middle French and Old French empestrer (“encumber”), influenced by English pest. The modern sense is an extension of the sense “infest”. Comparable to English construction pest + -er (used to form frequentative verbs).

• (UK) IPA^(key): /ˈpɛstə(ɹ)/
• (US) IPA^(key): /ˈpɛstɚ/, [ˈpʰɛstɚ]
• Rhymes: -ɛstə(ɹ)

pester (third-person singular simple present pesters, present participle pestering, simple past and past participle pestered)

1. (transitive) To bother, harass, or annoy persistently.

   Synonyms: badger, beleaguer, bug, hound, plague; see also Thesaurus:pester

   He pestered me with questions.

   She pestered him to help her.

2. (obsolete, transitive and intransitive) To crowd together thickly.

   Synonyms: cattle up, crowd, flock, huddle, throng

   • 1599, [Thomas] Nashe, Nashes Lenten Stuffe, […], London: […] [Thomas Judson and Valentine Simmes] for N[icholas] L[ing] and C[uthbert] B[urby] […], →OCLC, pages 5–6:

     That which eſpecialleſt nouriſht the moſt prime pleaſure in me, was after a ſtorme when they were driuen inſwarmes, and lay close peſtred together as thicke as they could packe; the next day following, if it were faire, they would cloud the whole skie with canuas, by ſpreading their drabled ſailes in the full clue abroad a drying, and make a brauer ſhew with them, then ſo many banners and ſtreamers diſplayed againſt the Sunne on a mountaine top.

• pest

pester (plural pesters)

1. A bother or nuisance.

   • 2017, Samuel J. Archer, Will There Be Another Lincoln, Nixon, Johnson or Kennedy?, page 15:

     By now I presumed I had become a real pester.

• Peters, Pretes, pestre, peters, pre-set, preset, serpet

pester

1. plural of post

From pesten +‎ -er.

• IPA^(key): /ˈpɛs.tər/
• Hyphenation: pes‧ter

pester m (plural pesters, diminutive pestertje n)

1. a bully (person who bullies or pesters somebody)

• pestkop

• pesten, pesterij

• perste, preest, streep

From peste +‎ -er.

• IPA^(key): /pɛs.te/

pester

1. to rant, curse, fulminate

• “pester”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012

• pertes, prêtes, prêtés

pester m or f

1. indefinite plural of pest

• pestar

pester m or f

1. indefinite feminine plural of pest

From Proto-Slavic *pьstrъ (“variegated”).

• IPA^(key): /pèːstər/

pẹ́stər (comparative pẹ́strejši, superlative nȁjpẹ́strejši)

1. colourful, variegated

Hard
	masculine	feminine	neuter
nom. sing.	péster	péstra	péstro
singular
	masculine	feminine	neuter
nominative	péster ind péstri def	péstra	péstro
genitive	péstrega	péstre	péstrega
dative	péstremu	péstri	péstremu
accusative	nominativeinan or genitiveanim	péstro	péstro
locative	péstrem	péstri	péstrem
instrumental	péstrim	péstro	péstrim
dual
	masculine	feminine	neuter
nominative	péstra	péstri	péstri
genitive	péstrih	péstrih	péstrih
dative	péstrima	péstrima	péstrima
accusative	péstra	péstri	péstri
locative	péstrih	péstrih	péstrih
instrumental	péstrima	péstrima	péstrima
plural
	masculine	feminine	neuter
nominative	péstri	péstre	péstra
genitive	péstrih	péstrih	péstrih
dative	péstrim	péstrim	péstrim
accusative	péstre	péstre	péstra
locative	péstrih	péstrih	péstrih
instrumental	péstrimi	péstrimi	péstrimi

• “pester”, in Slovarji Inštituta za slovenski jezik Frana Ramovša ZRC SAZU, portal Fran
• “pester”, in Termania, Amebis
• See also the general references