“Call him Voldemort, Harry. Always use the proper name for things. Fear of a name increases fear of the thing itself.”
-- Albus Dumbledore (PS17)
While discussing the fate of the Sorcerer’s Stone with Harry in the Hospital Wing, Dumbledore encourages Harry to use Voldemort’s name: “Fear of a name increases fear of the thing itself.” Harry has not encountered that opinion prior to this moment, but he accepts the advice readily.
When Hagrid initially explains to Harry about his parents’ killer and the reason for his fame in the Wizarding World, he struggles to say the name “Voldemort” aloud. Because the name is so widely feared and dreaded, few witches and wizards who understood its legacy would speak it–noteworthy exceptions being Dumbledore and (openly, once given Dumbledore’s permission at this moment) Harry. Saying “Voldemort” became an awe-inspiring, almost political statement. Voldemort’s followers refer to him more reverently as “My Lord,” “Master,” or “The Dark Lord,” while most who fear him called him “You-Know-Who” or (the wordier, arguably more polite) “He-Who-Must-Not-Be-Named.”
While those who fear the name shudder any time Harry says it in their presence, saying the name also affords him respect. Hermione picks up on this and uses it to her advantage by saying the name for the first time while trying to persuade Harry to lead the defensive organization later named Dumbledore’s Army. Ron eventually, reluctantly, follows suit, and many members of the Order of the Phoenix do as well. Seeing this as a sign of disrespect but also cunningly using the knowledge to his advantage, Voldemort places a Taboo on the name shortly after Dumbledore’s death. The Taboo allows Death Eaters to track Harry, Ron, and Hermione on Tottenham Court Road after the abrupt end of Bill and Fleur’s wedding and the fall of the Ministry of Magic. Either instinctively or coincidentally, Ron grows uneasy with the name and demands that Harry and Hermione refrain from using it, which saves them from repeated discovery until they learn about the Taboo when Ron leaves them and returns with the information. Harry accidentally says the name while attempting to convince Hermione and Ron that Voldemort is after the Elder Wand, which results in their capture by the Snatchers and delivery to Malfoy Manor.
Notably, acromantulas also fearfully refuse to speak the name “basilisk,” which results in Harry and Ron’s continued puzzlement regarding the source of the petrified students after their encounter in the Forbidden Forest and prior to finding Hermione’s note in the hospital wing.
From a psychological perspective, this quote from Dumbledore makes sense because it is understood that identifying and naming one’s fears can allow one to investigate and address them. Dumbledore does not fear death; he is an exceptionally brave wizard. So what kind of experiences may have led to this insight? We can only speculate. It is very possible that he merely observed the growing societal fear as most of the Wizarding World began to refrain from using Voldemort’s name. However, on a more abstract level, it could also be tied to his own reticence about the sorrows of his youth–his understanding that unspoken truths can fester, and that those truths have ways of manifesting themselves with or without permission or intent. Just as the Dursleys were unable to squash the magic out of Harry, who performed many instances of accidental magic, Credence Barebone was unable to contain his Obscurus, which killed his mother and Senator Shaw, Jr. Dumbledore lived through both events and likely numerous others, considering that his sister is speculated to have been an Obscurus as well, and that his relationship with Grindelwald seemingly prevented him from stopping his rise to power at the earliest opportunity.